Respiratory gas humidification system

ABSTRACT

A humidification system comprises a first sensor and a second sensor. The first and second sensors are adapted to sense flow characteristics within the system. The first and second sensors are isolated from the flow by barriers formed by respective first and second sealing members. The sealing members extend through apertures formed in the system and have a portion that contacts the sensing elements of the respective first and second sensors. A cartridge can hold the sensors and provide repeatable penetration depths into a flow passage of the system. A medical tube has a composite structure made of two or more distinct components that are spirally wound to form an elongate tube. One component can be a spirally wound elongate hollow body; the other component can be an elongate structural component spirally wound between turns of the spirally wound hollow body.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/936,309, filed Mar. 26, 2018, which is a continuation of U.S.application Ser. No. 14/485,608, filed Sep. 12, 2014, now U.S. Pat. No.9,987,455, which is a continuation of PCT International Application No.PCT/NZ2013/000042, filed Mar. 15, 2013, which claims priority to U.S.Provisional Application Nos. 61/733,360, filed Dec. 4, 2012; 61/733,359,filed Dec. 4, 2012; 61/611,331, filed Mar. 15, 2012; and 61/722,659,filed Nov. 5, 2012, the entirety of each of which is hereby incorporatedby reference herein.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention generally relates to respiratory methods ordevices and methods and devices for providing heated and humidifiedgases to a user. More particularly, the present invention relates totechniques for measuring flow characteristics within such devices andtubes for use in medical circuits suitable for providing gases to and/orremoving gases from a patient, such as in positive airway pressure(PAP), respirator, anaesthesia, ventilator, and insufflation systems.

Description of the Related Art

Many gas humidification systems deliver heated and humidified gases forvarious medical procedures, including respiratory treatment, laparoscopyand the like. These systems can be configured to control temperature,humidity and flow rates.

To provide a desired level of control, sensors must be used to detectflow characteristics. These sensors often are inserted directly into theflow and, because the sensors are not isolated from the fluid exchangeswith the patient, the sensors must be cleaned or discarded. In otherwords, the sensors cannot be reused immediately after disconnection fromthe first patient. Such systems are described, for example, in U.S. Pat.No. 6,584,972, which is hereby incorporated by reference in itsentirety.

Gas humidification systems also include medical circuits includingvarious components to transport the heated and/or humidified gases toand from patients. For example, in some breathing circuits such as PAPor assisted breathing circuits, gases inhaled by a patient are deliveredfrom a heater-humidifier through an inspiratory tube. As anotherexample, tubes can deliver humidified gas (commonly CO₂) into theabdominal cavity in insufflation circuits. This can help prevent “dryingout” of the patient's internal organs, and can decrease the amount oftime needed for recovery from surgery. Unheated tubing allowssignificant heat loss to ambient cooling. This cooling may result inunwanted condensation or “rainout” along the length of the tubingtransporting warm, humidified air. A need remains for tubing thatinsulates against heat loss and, for example, allows for improvedtemperature and/or humidity control in medical circuits. Accordingly, itis an object of certain features, aspects and advantages of theinvention to overcome or ameliorate one or more of the disadvantages ofthe prior art or to at least provide the public with a useful choice.

SUMMARY OF THE INVENTION

Thus, humidification apparatuses are described herein that willfacilitate sensing of liquid level in a humidification chamber and flowcharacteristics in a fluid flow while reducing waste and facilitatingmoderate reuse of certain components. Medical tubes and methods ofmanufacturing medical tubes are also disclosed herein in variousembodiments. Certain features, aspects and advantages of the presentinvention go some way to overcoming the above-described disadvantagesand/or at least provide the public with a useful choice.

In some configurations, a humidification apparatus comprises apressurized gas source. The pressurized gas source comprises an outlet.The outlet of the pressurized gas source is connected to an inlet to ahumidification unit. The humidification unit comprises an outlet. Theoutlet of the humidification unit is connected to a delivery component.A flow passage is defined between the pressurized gas source and thedelivery component. A sensor is adapted to sense a flow characteristicwithin the flow passage. The flow passage comprises an aperture. Thesensor extends through the aperture into the flow passage. The sensorcomprises a sensing portion. A barrier is positioned between the flowpassage and the sensor. The barrier contacts the sensing portion of thesensor with the barrier comprising a substantially constant thickness inthe region contacting the sensing portion.

In some configurations, the humidification unit comprises ahumidification chamber with the humidification chamber comprising a portand the aperture extending through a wall that defines at least aportion of the port.

In some configurations, the sensor comprises a first thermistor and asecond thermistor. The barrier comprises a first sleeve that receivesthe first thermistor and a second sleeve that receives the secondthermistor. In some configurations, two thermistors can be positionedwithin a single barrier.

In some configurations, the first thermistor is heated and the secondthermistor is non-heated.

In some configurations, the barrier comprises a mounting portion, afirst thickness and a second thickness that is less than the firstthickness. The second thickness is located adjacent to the sensingportion of the sensor. A region having the first thickness is positionedbetween the mounting portion and the portion having the secondthickness.

In some configurations, the barrier comprises a tip portion and amounting portion. The mounting portion secures the barrier within theaperture and the tip portion comprises a reduced thickness.

In some configurations, the barrier pneumatically seals the aperture andreceives at least a portion of the sensor such that the sensing portioncan be positioned within the flow passage and a mounting portion ispositioned outside of the flow passage.

In some configurations, the sensor is supported by a cartridge. Thehumidification unit comprises a humidification chamber. The cartridgeand the humidification chamber are removably attached and comprise aninterlocking connector.

In some configurations, the cartridge comprises a connector that isadapted to make electrical connection with the humidification unit whenthe cartridge is mounted to the humidification chamber and thehumidification chamber is mounted to the humidification unit.

In some configurations, the cartridge supports the sensor in arepeatable manner relative to a portion of the flow passage through thehumidification chamber such that the sensing portion of the sensor isconsistently positioned with repeated removal and replacement of thecartridge from the humidification chamber.

In some configurations, the barrier comprises a generally cylindricalbase and a generally bell-shaped head.

In some configurations, the generally bell-shaped head comprises aplurality of deflectable ribs.

In some configurations, the plurality of ribs are triangular andpositioned around a perimeter of the bell-shaped head.

In some configurations, one or more of the plurality of ribs has a widthof rib to width of separation ratio of about 3.7.

In some configurations, a humidification chamber comprises an outer bodydefining a chamber. An inlet port comprises a wall defining a passageinto the chamber. An outlet port comprises a wall defining a passage outof the chamber. The wall of the inlet port comprises a first aperture.The first aperture receives a first sealing member. The first sealingmember pneumatically seals the first aperture that extends through thewall of the inlet port. The wall of the outlet port comprises a secondaperture. The second aperture receives a second sealing member. Thesecond sealing member pneumatically seals the second aperture thatextends through the wall of the outlet port. A cartridge is removablyattachable to the outer body of the chamber with an interlockingstructure. The cartridge supports a first sensor that is receivablewithin the first seal and that extends through the first aperture. Thecartridge supports a second sensor that is receivable within the secondseal and that extends through the second aperture.

In some configurations, the first sensor comprises a first sensingcomponent and a second sensing component. The first sealing memberseparates the first sensing component from the second sensing component.

In some configurations, the first sensing component is a firstthermistor and the second sensing component is a second thermistor.

In some configurations, the first sealing member and the second sealingmember are removable.

In some configurations, the first sealing member has a contact portionthat is adapted to contact a sensing portion of the first sensor withthe contact portion having a reduced thickness.

In some configurations, the first sealing member has a contact portionthat is adapted to contact a sensing portion of the first sensor withthe contact portion having a substantially contact thickness.

In some configurations, the cartridge comprises an electrical connectorwith the electrical connector being electrically connected to the firstsensor and the second sensor.

In some configurations, the interlocking structure comprises a recessdefined on the outer body of the chamber and a boss defined on thecartridge.

Some embodiments provide for a chamber having a liquid level sensingsystem and being adapted to hold a conductive liquid. The chamberincludes a body comprising a non-conductive wall having an interiorsurface and an exterior surface, and a conductive base affixed to thenon-conductive wall to form a container adapted to hold liquids. Thechamber includes a sensor electrode positioned on the exterior surfaceof the non-conducting wall. The chamber includes a base electrodeelectrically coupled to the conductive base and positioned on anexterior surface of the conductive base. The chamber includes aconductive bridge attached to the interior surface of the non-conductingwall. The chamber includes a voltage source and a detection systemelectrically coupled to the sensor electrode. The conductive bridge andthe sensor electrode are capacitively coupled to one another in thechamber and the conductive bridge and the base electrode areconductively coupled to one another when the conductive liquid contactsboth the bridge and the base electrode. To determine a liquid level inthe chamber, the voltage source is configured to supply a varyingvoltage to the sensor electrode, and the detection system is configuredto determine a capacitance of the sensor electrode.

Some embodiments provide for a chamber having a liquid level sensingsystem and being adapted to hold a non-conductive liquid. The chamberincludes a body comprising a non-conductive wall having an interiorsurface and an exterior surface, and a conductive base affixed to thenon-conductive wall to form a container adapted to hold liquids. Thechamber includes a sensor electrode positioned on the exterior surfaceof the non-conducting wall. The chamber includes a base electrodeelectrically coupled to the conductive base and positioned on anexterior surface of the conductive base. The chamber includes aconductive bridge attached to the interior surface of the non-conductingwall. The chamber includes a voltage source and a detection systemelectrically coupled to the sensor electrode. The conductive bridge andthe sensor electrode are capacitively coupled to one another in thechamber and the conductive bridge and the base electrode arecapacitively coupled to one another. To determine a liquid level in thechamber, the voltage source is configured to supply a varying voltage tothe sensor electrode, and the detection system is configured todetermine a capacitance of the sensor electrode.

Some embodiments provide for a chamber having a liquid level sensingsystem and being adapted to hold a conductive liquid. The chamberincludes a body comprising a non-conductive wall having an interiorsurface and an exterior surface; a wicking material attached to theinterior surface of the non-conducting wall, the wicking material beingconfigured to allow the conductive liquid to move up the non-conductivewall through the wicking material; and a conductive base affixed to thenon-conductive wall to form a container adapted to hold liquids. Thechamber includes a sensor electrode positioned on the exterior surfaceof the non-conducting wall. The chamber includes a voltage source and adetection system electrically coupled to the sensor electrode. Thesensor electrode and the conductive liquid are capacitively coupled toone another. To determine a liquid level in the chamber, the voltagesource is configured to supply a varying voltage to the sensorelectrode, and the detection system is configured to determine acapacitance of the sensor electrode.

In some configurations a composite tube usable in various medicalcircuits includes a first elongate member comprising a spirally woundelongate hollow body and a second elongate member comprising an elongatestructural component spirally wound between turns of the spirally woundhollow body. The first elongate member can form in longitudinalcross-section a plurality of bubbles with a flattened surface at thelumen. Adjacent bubbles can be separated by a gap above the secondelongate member, or may not be directly connected to each other. Thebubbles can have perforations. In some configurations, a “double bubble”tube includes a plurality of bubbles, for example, two adjacent wraps ofthe first elongate member, between wraps of the second elongate member.The second elongate member can have a longitudinal cross-section that iswider proximal the lumen and narrower at a radial distance from thelumen. Specifically, the second elongate member can have a longitudinalcross-section that is generally triangular, generally T-shaped, orgenerally Y-shaped. One or more conductive filaments can be embedded orencapsulated in the second elongate member. The one or more conductivefilaments can be heating filaments (or more specifically, resistanceheating filaments) and/or sensing filaments. The tube can comprise pairsof conductive filaments, such as two or four conductive filaments. Pairsof conductive filaments can be formed into a connecting loop at one endof the composite tube. The one or more conductive filaments can bespaced from the lumen wall. In at least one embodiment, the secondelongate member can have a longitudinal cross-section that is generallytriangular, generally T-shaped, or generally Y-shaped, and one or moreconductive filaments can be embedded or encapsulated in the secondelongate member on opposite sides of the triangle, T-shape, or Y-shape.

In some configurations, a humidification apparatus comprises apressurized gas source comprising an outlet. An outlet of thepressurized gas source is connected to an inlet to a humidificationunit. The humidification unit comprises an outlet. The outlet of thehumidification unit is connected to a delivery component. A flow passageis defined between the pressurized gas source and the deliverycomponent. A sensor is adapted to sense a flow characteristic within theflow passage. The flow passage comprises an aperture. The sensor extendsthrough the aperture into the flow passage. The sensor comprises asensing portion. A barrier is positioned between the flow passage andthe sensor. The barrier contacts the sensing portion of the sensor withthe barrier comprising a substantially constant thickness in the regioncontacting the sensing portion.

In some configurations, the humidification unit comprises ahumidification chamber. The humidification chamber comprises a port andthe aperture extends through a wall that defines at least a portion ofthe port.

In some configurations, the sensor comprises a first thermistor and asecond thermistor. The barrier comprises a first sleeve that receivesthe first thermistor and a second sleeve that receives the secondthermistor.

In some configurations, the first thermistor is heated and the secondthermistor is non-heated.

In some configurations, the barrier comprises a mounting portion, afirst thickness and a second thickness that is less than the firstthickness. The second thickness is located adjacent to the sensingportion of the sensor and a region having the first thickness ispositioned between the mounting portion and the portion having thesecond thickness.

In some configurations, the barrier comprises a tip portion and amounting portion. The mounting portion secures the barrier within theaperture and the tip portion comprises a reduced thickness.

In some configurations, the barrier pneumatically seals the aperture andreceives at least a portion of the sensor such that the sensing portioncan be positioned within the flow passage and a mounting portion can bepositioned outside of the flow passage.

In some configurations, the sensor is supported by a cartridge. Thehumidification unit comprises a humidification chamber. The cartridgeand the humidification chamber can be removably attached and cancomprise an interlocking connector.

In some configurations, the cartridge comprises a connector that isadapted to make electrical connection with the humidification unit whenthe cartridge is mounted to the humidification chamber and thehumidification chamber is mounted to the humidification unit.

In some configurations, the cartridge supports the sensor in arepeatable manner relative to a portion of the flow passage through thehumidification chamber such that the sensing portion of the sensor isconsistently positioned with repeated removal and replacement of thecartridge from the humidification chamber.

In some configurations, a humidification chamber comprises an outer bodydefining a chamber. An inlet port comprises a wall that defines apassage into the chamber. An outlet port comprises a wall that defines apassage out of the chamber. The wall of the inlet port comprises a firstaperture. The first aperture receives a first sealing member. The firstsealing member pneumatically seals the first aperture that extendsthrough the wall of the inlet port. The wall of the outlet portcomprises a second aperture. The second aperture receives a secondsealing member. The second sealing member pneumatically seals the secondaperture that extends through the wall of the outlet port. A cartridgeis removably attachable to the outer body of the chamber with aninterlocking structure. The cartridge supports a first sensor that isreceivable within the first seal and that extends through the firstaperture. The cartridge supports a second sensor that is receivablewithin the second seal and that extends through the second aperture.

In some configurations, the first sensor comprises a first sensingcomponent and a second sensing component. The first sealing memberseparates the first sensing component from the second sensing component.

In some configurations, the first sensing component is a firstthermistor and the second sensing component is a second thermistor.

In some configurations, the first sealing member and the second sealingmember are removable.

In some configurations, the first sealing member has a contact portionthat is adapted to contact a sensing portion of the first sensor. Thecontact portion has a reduced thickness.

In some configurations, the first sealing member has a contact portionthat is adapted to contact a sensing portion of the first sensor. Thecontact portion has a substantially contact thickness.

In some configurations, the cartridge comprises an electrical connector.The electrical connector is electrically connected to the first sensorand the second sensor.

In some configurations, the interlocking structure comprises a recessdefined on the outer body of the chamber and a boss defined on thecartridge.

In some configurations, the chamber has a liquid level sensing systemand is adapted to hold a conductive liquid. The chamber comprises a bodyincluding a non-conductive wall having an interior surface, an exteriorsurface and a conductive base affixed to the non-conductive wall to forma container adapted to hold liquids. A sensor electrode can bepositioned on the exterior surface of the non-conducting wall. A baseelectrode can be electrically coupled to the conductive base and can bepositioned on an exterior surface of the conductive base. A conductivebridge can be attached to the interior surface of the non-conductingwall. The conductive bridge can be capacitively coupled to the sensorelectrode. The conductive bridge and the base electrode can beconductively coupled when the conductive liquid contacts both the bridgeand the base electrode. A voltage source can be electrically coupled tothe sensor electrode and can be configured to supply a varying voltageto the sensor electrode. A detection system can be electrically coupledto the sensor electrode and can be configured to determine a capacitanceof the sensor electrode.

In some configurations, the sensor electrode is positioned further fromthe conductive base than the conductive bridge such that at least aportion of the sensor electrode extends beyond the conductive bridge ina direction away from the conductive base.

In some configurations, the detection system is configured to detect achange in the capacitance of the sensor electrode when a level of theconducting liquid is higher than the conducting bridge.

In some configurations, the detection system is configured to detect achange in the capacitance of the sensor electrode when a level of theconducting liquid is below the sensor electrode.

In some configurations, the sensor electrode is larger than theconductive base.

In some configurations, the base electrode is electrically coupled to anelectrical ground.

In some configurations, the conductive base provides a virtualelectrical ground to the liquid level sensing system.

In some configurations, the voltage source comprises an alternatingcurrent voltage source.

In some configurations, the capacitance of the sensor electrodeincreases by a discrete amount when the conducting liquid contacts theconducting bridge.

In some configurations, A humidification unit incorporates the chamberas discussed above.

In some configurations, a chamber has a liquid level sensing system andis adapted to hold a non-conductive liquid. The chamber comprises a bodycomprising a non-conductive wall having an interior surface and anexterior surface and a conductive base affixed to the non-conductivewall to form a container adapted to hold liquids. A sensor electrode canbe positioned on the exterior surface of the non-conducting wall. A baseelectrode can be electrically coupled to the conductive base and can bepositioned on an exterior surface of the conductive base. A conductivebridge can be attached to the interior surface of the non-conductingwall. A voltage source electrically can be coupled to the sensorelectrode. A detection system can be electrically coupled to the sensorelectrode. The conductive bridge and the sensor electrode can becapacitively coupled. The conductive bridge and the base electrode canbe capacitively coupled. The voltage source can be configured to supplya varying voltage to the sensor electrode. The detection system can beconfigured to determine a capacitance of the sensor electrode.

In some configurations, the detection system is further configured todetermine a liquid level corresponding to the capacitance of the sensorelectrode.

In some configurations, the detection system is configured to determineat least one of an out-of-liquid condition or an overfill condition.

In some configurations, the detection system is further configured toprovide a notification corresponding to the liquid level.

In some configurations, the sensor electrode is removably attached tothe exterior surface of the non-conducting wall.

In some configurations, a humidification unit incorporates the chamberas described above.

In some configurations, a chamber has a liquid level sensing system andis adapted to hold a conductive liquid. The chamber comprises a bodycomprising a non-conductive wall having an interior surface and anexterior surface. A wicking material can be attached to the interiorsurface of the non-conducting wall. The wicking material can beconfigured to allow the conductive liquid to move up the non-conductivewall through the wicking material. A conductive base can be affixed tothe non-conductive wall to form a container adapted to hold liquids. Asensor electrode can be positioned on the exterior surface of thenon-conducting wall. A voltage source can be electrically coupled to thesensor electrode. A detection system can be electrically coupled to thesensor electrode. The sensor electrode and the conductive liquid can becapacitively coupled. The voltage source can be configured to supply avarying voltage to the sensor electrode. The detection system can beconfigured to determine a capacitance of the sensor electrode.

In some configurations, the detection system is configured to determinean out-of-liquid condition when no conducting liquid is in the chamber.

In some configurations, the detection system is configured to provide anotification when the out-of-liquid condition is determined.

In some configurations, a humidification unit can incorporating thechamber as described above.

In some configurations, a composite tube comprises a first elongatemember comprising a hollow body spirally wound to form at least in partan elongate tube having a longitudinal axis. A lumen extends along thelongitudinal axis. A hollow wall surrounds the lumen. A second elongatemember is spirally wound and joined between adjacent turns of the firstelongate member. The second elongate member forms at least a portion ofthe lumen of the elongate tube.

In some configurations, the first elongate member is a tube.

In some configurations, the first elongate member forms in longitudinalcross-section a plurality of bubbles with a flattened surface at thelumen.

In some configurations, adjacent bubbles are separated by a gap abovethe second elongate member.

In some configurations, adjacent bubbles are not directly connected toeach other.

In some configurations, the bubbles have perforations.

In some configurations, the second elongate member has a longitudinalcross-section that is wider proximal the lumen and narrower at a radialdistance from the lumen.

In some configurations, the second elongate member has a longitudinalcross-section that is generally triangular.

In some configurations, the second elongate member has a longitudinalcross-section that is generally T-shaped or Y-shaped.

In some configurations, one or more conductive filaments can be embeddedor encapsulated in the second elongate member.

In some configurations, the conductive filament is heating filament.

In some configurations, the conductive filament is sensing filament.

In some configurations, two conductive filaments can be embedded orencapsulated in the second elongate member.

In some configurations, four conductive filaments can be embedded orencapsulated in the second elongate member.

In some configurations, pairs of conductive filaments are formed into aconnecting loop at one end of the composite tube.

In some configurations, the second elongate member has a longitudinalcross-section that is generally triangular, generally T-shaped, orgenerally Y-shaped, and the one or more conductive filaments areembedded or encapsulated in the second elongate member on opposite sidesof the triangle, T-shape, or Y-shape.

In some configurations, the one or more filaments are spaced from thelumen wall.

In some configurations, a medical circuit component comprises thecomposite tube described above.

In some configurations, an inspiratory tube comprises the composite tubedescribed above.

In some configurations, an expiratory tube comprises the composite tubedescribed above.

In some configurations, a PAP component comprises the composite tubedescribed above.

In some configurations, an insufflation circuit component comprises thecomposite tube described above.

In some configurations, an exploratory component comprises the compositetube described above.

In some configurations, a surgical component comprises the compositetube described above.

In some configurations, a method of manufacturing a composite tubecomprises: providing a first elongate member comprising a hollow bodyand a second elongate member configured to provide structural supportfor the first elongate member; spirally wrapping the second elongatemember around a mandrel with opposite side edge portions of the secondelongate member being spaced apart on adjacent wraps, thereby forming asecond-elongate-member spiral; and spirally wrapping the first elongatemember around the second-elongate-member spiral, such that portions ofthe first elongate member overlap adjacent wraps of thesecond-elongate-member spiral and a portion of the first elongate memberis disposed adjacent the mandrel in the space between the wraps of thesecond-elongate-member spiral, thereby forming a first-elongate-memberspiral.

In some configurations, the method further comprises supplying air at apressure greater than atmospheric pressure to an end of the firstelongate member.

In some configurations, the method further comprises cooling thesecond-elongate-member spiral and the first-elongate-member spiral toform a composite tube having a lumen extending along a longitudinal axisand a hollow space surrounding the lumen.

In some configurations, the method further comprises forming the secondelongate member.

In some configurations, the method further comprises forming the secondelongate member comprises extruding the second elongate member with asecond extruder.

In some configurations, the method further comprises the second extruderis configured to encapsulate one or more conductive filaments in thesecond elongate member.

In some configurations, the method further comprises forming the secondelongate member comprises embedding conductive filaments in the secondelongate member.

In some configurations, the method further comprises the conductivefilaments are non-reactive with the second elongate member.

In some configurations, the method further comprises the conductivefilaments comprise aluminum or copper.

In some configurations, the method further comprises forming pairs ofconductive filaments into a connecting loop at one end of the compositetube.

In some configurations, the method further comprises forming the firstelongate member.

In some configurations, the method further comprises forming the firstelongate member comprises extruding the first elongate member with afirst extruder.

In some configurations, the method further comprises the first extruderis distinct from the second extruder.

In some configurations, a medical tube comprises an elongate hollow bodyspirally wound to form an elongate tube having a longitudinal axis. Alumen extends along the longitudinal axis. A hollow wall surrounds thelumen. The elongate hollow body has in transverse cross-section a walldefining at least a portion of the hollow body. A reinforcement portionextends along a length of the elongate hollow body and is spirallypositioned between adjacent turns of the elongate hollow body. Thereinforcement portion forms a portion of the lumen of the elongate tube.The reinforcement portion is relatively thicker or more rigid than thewall of the elongate hollow body.

In some configurations, the reinforcement portion is formed from thesame piece of material as the elongate hollow body.

In some configurations, the elongate hollow body in transversecross-section comprises two reinforcement portions on opposite sides ofthe elongate hollow body, wherein spiral winding of the elongate hollowbody joins adjacent reinforcement portions to each other such thatopposite edges of the reinforcement portions touch on adjacent turns ofthe elongate hollow body.

In some configurations, opposite side edges of the reinforcementportions overlap on adjacent turns of the elongate hollow body.

In some configurations, the reinforcement portion is made of a separatepiece of material than the elongate hollow body.

In some configurations, the hollow body forms in longitudinalcross-section a plurality of bubbles with a flattened surface at thelumen.

In some configurations, the bubbles have perforations.

In some configurations, one or more conductive filaments embedded orencapsulated within the reinforcement portion.

In some configurations, the conductive filament is heating filament.

In some configurations, the conductive filament is sensing filament.

In some configurations, two conductive filaments are included, whereinone conductive filament is embedded or encapsulated in each of thereinforcement portions.

In some configurations, two conductive filaments are positioned on onlyone side of the elongate hollow body.

In some configurations, pairs of conductive filaments are formed into aconnecting loop at one end of the elongate tube.

In some configurations, the one or more filaments are spaced from thelumen wall.

In some configurations, a medical circuit component comprises themedical tube described above.

In some configurations, an inspiratory tube comprises the medical tubedescribed above.

In some configurations, an expiratory tube comprises the medical tubedescribed above.

In some configurations, a PAP component comprises the medical tubedescribed above.

In some configurations, an insufflation circuit component comprises themedical tube described above.

In some configurations, an exploratory component comprises the medicaltube described above.

In some configurations, a surgical component comprises the medical tubedescribed above.

In some configurations, a method of manufacturing a medical tubecomprises: spirally winding an elongate hollow body around a mandrel toform an elongate tube having a longitudinal axis, a lumen extendingalong the longitudinal axis, and a hollow wall surrounding the lumen,wherein the elongate hollow body has in transverse cross-section a walldefining at least a portion of the hollow body and two reinforcementportions on opposite sides of the elongate body forming a portion of thewall of the lumen, the two reinforcement portions being relativelythicker or more rigid than the wall defining at least a portion of thehollow body; and joining adjacent reinforcement portions to each othersuch that opposite edges of the reinforcement portions touch on adjacentturns of the elongate hollow body.

In some configurations, the method further comprises joining adjacentreinforcement portions to each other causes edges of the reinforcementportions to overlap.

In some configurations, the method further comprises supplying air at apressure greater than atmospheric pressure to an end of the elongatehollow body.

In some configurations, the method further comprises cooling theelongate hollow body to join the adjacent reinforcement portions to eachother.

In some configurations, the method further comprises extruding theelongate hollow body.

In some configurations, the method further comprises embeddingconductive filaments in the reinforcement portions.

In some configurations, the method further comprises forming pairs ofconductive filaments into a connecting loop at one end of the elongatetube.

For purposes of summarizing the invention, certain aspects, advantagesand novel features of the invention have been described herein. It is tobe understood that not necessarily all such advantages may be achievedin accordance with any particular embodiment of the invention. Thus, theinvention may be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as may be taught or suggestedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will be described with reference to the following drawings,which are illustrative but should not be limiting of the presentinvention.

FIG. 1 is a simplified view of a humidification system arranged andconfigured in accordance with certain features, aspects and advantagesof the present invention.

FIG. 1A is a simplified view of a humidification system.

FIG. 1B is an insufflation system according to at least one embodiment.

FIG. 2 is a side elevation view of a humidification chamber that isarranged and configured for use with certain features, aspects andadvantages of the present invention.

FIG. 2A illustrates a block diagram of a liquid level sensing systemincorporated with a controller of a humidification system.

FIG. 2B illustrates an example liquid level sensing system in ahumidification chamber with accompanying voltage source and detectionsystem.

FIG. 2C illustrates an example liquid level sensing system in ahumidification chamber having a wicking material along an interior wall.

FIG. 2D illustrates a flow chart of an example method of detectingliquid levels in a humidification chamber.

FIG. 3 is a perspective view of the humidification chamber of FIG. 2with seals inserted into apertures formed in ports of the humidificationchamber.

FIG. 4 is a sectioned view through one of the seals and an inlet port ofthe humidification chamber.

FIG. 5 is a top view of the seal of FIG. 4, which is substantially thesame as the bottom view of the seal.

FIG. 6 is a side view of the seal of FIG. 4, which is substantially thesame as the opposing side view of the seal.

FIG. 7 is a front view of the seal of FIG. 4.

FIG. 8 is a rear view of the seal of FIG. 4.

FIG. 9 is a perspective view of the seal of FIG. 4.

FIG. 10 is a sectioned view through one of the seals and an outlet portof the humidification chamber.

FIG. 11 is a side view of the seal of FIG. 10, which is substantiallythe same as the opposing side view of the seal.

FIG. 12 is a top view of the seal of FIG. 10, which is substantially thesame as the bottom view of the seal.

FIG. 13 is a front view of the seal of FIG. 10.

FIG. 14 is a rear view of the seal of FIG. 10.

FIG. 15 is a perspective view of the seal of FIG. 10.

FIG. 16 is an exploded perspective view of the seals of FIGS. 4 and 10together with corresponding sensors.

FIG. 17 is a partial sectioned view of a chamber having a port with asleeve and a biased sensor.

FIG. 18A is a perspective view of a seal.

FIG. 18B is a side view of the seal of FIG. 18A.

FIG. 18C is another perspective view of the seal of FIG. 18A.

FIG. 18D is a sectioned view of the seal of FIG. 18A.

FIG. 18E is a perspective view of the seal of FIG. 18A shown on a portof a humidification chamber.

FIG. 18F is another perspective view of the seal and chamber of FIG.18E.

FIG. 18G is another perspective view of the seal and chamber of FIG.18E.

FIG. 19A is a side view of a seal.

FIG. 19B is a section view of the seal of FIG. 19A.

FIG. 19C is a perspective view of the seal of FIG. 19A.

FIG. 20A is a side view of a seal.

FIG. 20B is a side view of a seal.

FIG. 20C is a side view of a seal.

FIG. 21 is a perspective view of a cartridge with the sensors attached.

FIG. 22 is another perspective view of the cartridge and sensors.

FIG. 23 is top view of the cartridge and sensors.

FIG. 24 is a rear view of the cartridge and sensors.

FIG. 25 is a left side view of the cartridge and sensors.

FIG. 26 is a front view of the cartridge.

FIG. 27 is right side view of the cartridge and sensors.

FIG. 28 is bottom view of the cartridge and sensors.

FIG. 29 is a perspective view of the cartridge assembled to thehumidification chamber.

FIG. 30 is a top view of the cartridge assembled to the humidificationchamber.

FIG. 31 is front view of the cartridge assembled to the humidificationchamber.

FIG. 32 is a right side view of the cartridge assembled to thehumidification chamber.

FIG. 33 is a rear view of the cartridge assembled to the humidificationchamber.

FIG. 34 is a left side view of the cartridge assembled to thehumidification chamber.

FIG. 35 is an exploded perspective view showing the cartridge beingassembled to the humidification chamber.

FIG. 36 is an exploded perspective view showing an alternative cartridgebeing assembled to an alternative humidification chamber.

FIG. 37A shows a side-plan view of a section of an example compositetube.

FIG. 37B shows a longitudinal cross-section of a top portion a tubesimilar to the example composite tube of FIG. 37A.

FIG. 37C shows another longitudinal cross-section illustrating a firstelongate member in the composite tube.

FIG. 37D shows another longitudinal cross-section of a top portion of atube.

FIG. 37E shows another longitudinal cross-section of a top portion of atube.

FIG. 37F shows a tube with a portion exposed in longitudinalcross-section.

FIG. 37G shows a longitudinal cross-section of a portion of a tubesimilar to the example tube of FIG. 37F.

FIGS. 37H-L show variations of a tube adapted to provide increasedlateral stretch in the tube.

FIGS. 37V-Z show a stretched state of the tubes shown in FIGS. 37H-L,respectively.

FIG. 38A shows a front-plan cross-sectional schematic of a flexibilityjig.

FIG. 38B shows a detailed front-plan cross-sectional schematic ofrollers on the flexibility jig of FIG. 38A.

FIGS. 38C-38F show a flexibility jig in use. FIGS. 38C and 38E show afront-perspective view of samples under testing in the jig. FIGS. 38Dand 38F show a rear-perspective view of samples under testing in thejig.

FIG. 39A shows a crush resistance testing jig.

FIG. 39B shows a plot of load vs. extension, used for determining crushstiffness.

FIG. 40A shows a transverse cross-section of a second elongate member inthe composite tube.

FIG. 40B shows another transverse cross-section of a second elongatemember.

FIG. 40C shows another example second elongate member.

FIG. 40D shows another example second elongate member.

FIG. 40E shows another example second elongate member.

FIG. 40F shows another example second elongate member.

FIG. 40G shows another example second elongate member.

FIG. 40H shows an alternative embodiment of the second elongate member.

FIG. 41A shows an aspect in a method for forming the composite tube.

FIG. 41B shows a spiral-wound second elongate member.

FIG. 41C shows another aspect in a method for forming the compositetube.

FIG. 41D shows another aspect in a method for forming the compositetube.

FIG. 41E shows another aspect in a method for forming the compositetube.

FIG. 41F shows another aspect in a method for forming the compositetube.

FIGS. 41G-41I show example configurations of longitudinal cross sectionsof tubes.

FIGS. 41J-41Q show an alternative method of forming a tube.

FIGS. 42A-42B show another example illustrating a single elongate hollowbody being spirally wound to form a medical tube.

FIGS. 42C-42F show examples of other single elongate hollow bodies beingspirally wound to form a medical tube.

FIGS. 43A-43L show a general flow chart and more detailed schematics andphotographs relating to a method for attaching a connector to the end ofthe tube that is configured in use to connect to a humidifier.

FIGS. 44A-44I show schematics relating to a connector suitable forattaching a tube to a patient interface.

FIGS. 45A-45E show schematics relating to a connector suitable forattaching a tube to a humidifier port, patient interface, or any othersuitable component.

FIGS. 46A-46F show a connector which can be used for medical circuitshaving electrical wires running therethrough.

FIG. 47 is a schematic illustration of a coaxial tube, according to atleast one embodiment.

FIGS. 48A-48C show examples of first elongate member shapes configuredto improve thermal efficiency.

FIGS. 48D-48F show examples of filament arrangements configured toimprove thermal efficiency.

FIGS. 49A-49C show examples of first elongate member stacking.

FIGS. 50A-50D demonstrate radius of curvature properties of tubesaccording to various embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Certain embodiments and examples of humidification systems and/or liquidlevel sensing systems are described herein. Those of skill in the artwill appreciate that the disclosure extends beyond the specificallydisclosed embodiments and/or uses and obvious modifications andequivalents thereof. Thus, it is intended that the scope of thedisclosure herein disclosed should not be limited by any particularembodiments described herein.

Humidification System

FIGS. 1 and 1A illustrate a respiratory humidification system 20 thatcan include a sensing arrangement 22, liquid level sensing system 222,composite tubes, and/or other features arranged and configured inaccordance with certain features, aspects and advantages of the presentdisclosure. The sensing arrangement 22, sensing system 222, compositetubes, and other features are illustrated and described herein inconjunction with the respiratory humidification system 20 but can findapplicability in other applications involving the supply of a heated andhumidified gas flow to a user or patient, including but not limited tolaparoscopy, ventilation, and the like.

The illustrated respiratory humidification system 20 comprises apressurized gas source 30. In some applications, the pressurized gassource 30 comprises a fan, blower or the like. In some applications, thepressurized gas source 30 comprises a ventilator or other positivepressure generating device. The pressurized gas source 30 comprises aninlet 32 and an outlet 34.

The pressurized gas source 30 provides a flow of fluid (e.g., oxygen,anesthetic gases, air or the like) to a humidification unit 40. Thefluid flow passes from the outlet 34 of the pressurized gas source 30 toan inlet 42 of the humidification unit 40. In the illustratedconfiguration, the humidification unit 40 is shown separate of thepressurized gas source 30 with the inlet 42 of the humidification unit40 connected to the outlet 34 of the pressurized gas source 30 with aconduit 44. In some applications, the pressurized gas source 30 and thehumidification unit 40 can be integrated into a single housing.

While other types of humidification units can be used with certainfeatures, aspects and advantages of the present invention, theillustrated humidification unit 40 is a pass over humidifier thatcomprises a humidification chamber 46 and the inlet 42 to thehumidification unit 40 comprises an inlet to the humidification chamber46. In some configurations, the humidification chamber 46 comprises aplastic formed body 50 with a heat conductive base 52 sealed thereto. Acompartment can be defined within the humidification chamber 46. Thecompartment is adapted to hold a volume of water that can be heated byheat conducted through the base 52. In some applications, the base 52 isadapted to contact a heater plate 54. The heater plate 54 can becontrolled through a controller 56 or other suitable component such thatthe heat transferred into the water can be varied.

With reference to FIG. 2, in the illustrated configuration, the body 50of the humidification chamber 46 comprises a port 60 that defines theinlet 42 and the body 50 also comprises a port 62 that defines an outlet64 of the humidification chamber 46. In some configurations, one or moreof the ports 60, 62 can be formed on an end of a conduit or as aconnector. In some configurations, the ports 60, 62 can have a portionthat is received within an opening of the chamber. As water containedwithin the humidification chamber 46 is heated, water vapor is mixedwith gases introduced into the humidification chamber 46 through theinlet port 60. The mixture of gases and water vapor exits thehumidification chamber 46 through the outlet port 62.

With reference again to FIG. 1, an inspiratory conduit 70 or othersuitable gases transportation pathway can be connected to the outlet 64that defines the outlet port 62 of the humidification unit 40. Theconduit 70 conveys toward a user the mixture of gases and water vaporthat exits the humidification chamber 46. A condensation-reductioncomponent may be positioned along at least a portion of the conduit 70.In the illustrated configuration, the condensation-reduction componentcomprises a heating element 72 that is positioned along at least aportion of the conduit 70. The heating element 72 can raise or maintainthe temperature of the gases and water vapor mixture being conveyed bythe conduit 70. In some configurations, the heating element 72 can be awire that defines a resistance heater. Other configurations arepossible. By increasing or maintaining the temperature of the gases andwater vapor mixture, the water vapor is less likely to condensate out ofthe mixture.

A delivery component, such as an interface 74 for example but withoutlimitation, can be provided to connect the conduit 70 to the user. Inthe illustrated configuration, the interface 74 comprises a mask.Moreover, in the illustrated configuration, the interface 74 comprises amask that extends over the mouth and nose of the user. Any suitableinterface 74 can be used. In some applications, certain features,aspects and advantages of the present invention can be used withintubation components, laparoscopy components, insufflators or the like.In some applications, such as those used with a ventilator, a suitablefitting (e.g., a Y-piece 75) can be positioned between the user and theconduit 70 such that an expiratory conduit 71 can be connected betweenthe user and an inlet of the ventilator, for example but withoutlimitation.

As discussed above, the sensing arrangement 22, tubes, and otherfeatures illustrated and described herein can be used in conjunctionwith laparoscopic surgery, also called minimally invasive surgery orkeyhole surgery. During laparoscopic surgery with insufflation, it maybe desirable for the insufflation gas (commonly CO₂) to be humidifiedbefore being passed into the abdominal cavity. This can help reduce oreliminate the likelihood of “drying out” of the patient's internalorgans, and can decrease the amount of time needed for recovery fromsurgery. FIG. 1B illustrates an example embodiment of an insufflationsystem 701, which includes an insufflator 703 that produces a stream ofinsufflation gases at a pressure above atmospheric for delivery into thepatient 705 abdominal or peritoneal cavity. The gases pass into ahumidification unit 707, including a heater base 709 and humidifierchamber 711, with the chamber 711 in use in contact with the heater base709 so that the heater base 709 provides heat to the chamber 711. In thehumidifier 707, the insufflation gases are passed through the chamber711 so that they become humidified to an appropriate level of moisture.The system 701 includes a delivery conduit 713 that delivers humidifiedinsufflation gases from the humidifier chamber 711 to the patient 705peritoneal cavity or surgical site. A smoke evacuation system 715leading out of the body cavity of the patient 705 comprises a dischargeor exhaust limb 717, a discharge assembly 719, and a filter 721.

In some configurations, the delivery conduit 713 can also retain smokerather than using (or in addition to) a smoke evacuation system. Forexample, in some configurations, rather than evacuating smoke from thepatient's body cavity through an evacuation system, the smoke cansucked, withdrawn or guided into and back through the path of theconduit 713 (i.e. into and through the outer walls of the tube). Thepath 203 could include a filter/absorbent medium to receive the smoke.The conduit could be generally disposable after surgery so it does notneed to be cleaned afterwards. A valve or other type of dischargeassembly (e.g., discharge assembly 719) may be incorporated between thecavity and the path 203 to guide the smoke into the path after/duringsurgery.

Sensing and Control System

The controller 56 of the humidification unit 40 can control operation ofvarious components of the respiratory humidification system 20. Whilethe illustrated configuration is shown with a single controller 56,multiple controllers can be used in other configurations. The multiplecontrollers can communicate or can be provided separate functions and,therefore, the controllers need not communicate. In some configurations,the controller 56 may comprise a microprocessor, a processor or logiccircuitry with associated memory or storage that contains software codefor a computer program. In such configurations, the controller 56 cancontrol operation of the humidification system 20 in accordance withinstructions, such as contained within the computer program, and also inresponse to external inputs.

In some configurations, the controller 56 can receive input from aheater plate sensor 80. The heater plate sensor 80 can provide thecontroller 56 with information regarding the temperature and/or powerusage of the heater plate 54. In some configurations, another input tothe controller 56 can be a user input component 82. The user inputcomponent 82 can comprise a switch, dial, knob, or other suitablecontrol input device, including but not limited to touch screens and thelike. The user input component 82 can be operated by the user, ahealthcare professional or other person to set a desired temperature ofgases to be delivered to the user, a desired humidity level of gases tobe delivered or both. In some configurations, the user input component82 can be operated to control other operating characteristics of thehumidification system 20. For example, the user input component 82 cancontrol heating delivered by the heating element 72 or any desiredcharacteristic of the air flow (e.g., pressure, flow rate, etc.).

Liquid Level Sensing System

The controller 56 also receives input from the liquid level sensingsystem 222. The liquid level sensing system 222 can comprise one or moresensors positioned on or near the chamber 46 or base 52. The liquidlevel sensing system 222 can include a voltage source and a detectionsystem for determining liquid levels in the chamber 46, as describedherein. The controller 56 can receive liquid level information from theliquid level sensing system 222 and adjust control properties inresponse to the liquid level information. In some embodiments, thecontroller 56 can notify a user through the user interface component 82about liquid level conditions.

FIG. 2 illustrates an example humidification chamber 46 having a liquidlevel sensing system 222 according to some embodiments. The liquid levelsensing system 222 can include one or more sensors 200. The sensors 200can be positioned so that they are capacitively and/or conductivelycoupled to one another and/or to ground. The capacitance of one or moreof the sensors 200 can change in response to changes in liquid levels.The liquid level sensing system 222 can detect these changes anddetermine a fluid level or a fluid level condition (e.g., out of water,chamber overfill, etc.) based at least in part on the change incapacitance of one or more sensors 200.

The humidification chamber 46 can comprise a body 50 having at least onenon-conductive wall 53. The non-conductive wall 53 can be made of anysuitable material that does not effectively conduct electricity, such asan insulating material. The humidification chamber 46 comprises a base52 sealed to the body 50. The base 52 can be made of any suitableelectrically conductive material, any suitable electricallynon-conductive material, or a combination of electrically conductive andelectrically non-conductive materials. For example, the base 52 cancomprise a conductive material covered in a non-conductive material. Insome embodiments, the base 52 is made of an electrically non-conductivematerial where a base electrode 206 is present.

The liquid sensing system 222 includes a sensor electrode 202 positionedon or near an exterior surface of the non-conductive wall 53. The sensorelectrode 202 can be made of a conducting material, such as a metal. Thesensor electrode 202 can be attached to the non-conducting wall 53 usingany conventional means. In some embodiments, the sensor electrode 202 isremovably attached to the non-conducting wall 53 to allow repositioningof the sensor electrode 202 or to allow it to be used with a differenthumidification chamber 46.

The liquid sensing system 222 can include a bridge 204 attached to aninterior surface of the non-conducting wall 53. The bridge 204 is madeof a conducting material and is positioned on or near the interiorsurface of the non-conducting wall 53. In some embodiments, the bridge204 is affixed to the interior surface of the non-conducting wall 53using any conventional means such that the bridge 204 remainssubstantially stationary in response to changes in a level of liquid inthe chamber 46. The bridge 204 can be positioned relatively near aposition of the sensor electrode 202 on the exterior surface of thenon-conducting wall 53. The relative positions of the sensor electrode202 and the bridge 204 can be configured to produce a discrete andmeasurable increase in the capacitance of the sensor electrode 202 whena liquid contacts the bridge 204. A measurable change can be any changein capacitance that is detected by the fluid level sensing system 222,as described more fully herein. By placing the bridge 204 in the chamber46, a sudden and discrete increase in capacitance can be observed when aliquid contacts the bridge 204. It should be understood that the bridge204 is not electrically coupled to the sensor electrode 202 throughphysical connections or wired means, but is capacitively coupled to thesensor electrode 202 based at least in part on the electrical propertiesof each and/or their physical proximity. Furthermore the bridge 204 isnot electrically coupled to any other component of the liquid levelsensing system 222 through wired means. Instead, the bridge 204 can becapacitively coupled to a base electrode 206 where the chamber 46contains a non-conductive liquid or the bridge 204 can be conductivelycoupled to the base electrode 206 where the chamber 46 contains aconductive liquid that provides an electrically conductive path betweenthe bridge 204 and the base 52. Thus, there are no wires or cablespassing from outside of the chamber 46 to inside of the chamber 46 aswith other systems having a sensor placed inside a chamber. This allowsthe structure of the humidification chamber 46 to remain free frompathways for cables or wires which pass from the exterior to theinterior of the chamber 46 (which may require sealing to prevent losingfluids through the pathways) when using the liquid level sensing system222 described herein.

The liquid level sensing system 222 can include a base electrode 206positioned on the base 52 of the humidification chamber 46. In someembodiments, the base 52 acts as a virtual electrical ground for thefluid level sensing system 222 meaning that it is not electricallycoupled to an electrical ground but provides a virtual electrical groundto the system 222. In some embodiments, the base electrode 206 iscoupled to an electrical ground through the base 52 (e.g., the base 52can provide a virtual ground or it can be electrically coupled toground), through an electrical circuit, or through some other means.

In some embodiments, the sensor electrode 202 is not positioned oppositethe bridge 204 as illustrated in FIG. 2. The sensor electrode 202 can bepositioned in other locations and/or moved relative to the bridge 204and still experience a discrete and measurable change in capacitance asdescribed herein. This is due at least in part to the change incapacitance of the sensor electrode 202 when liquid contacts the bridge204. This allows for flexible positioning of the sensor electrode 202.The sensor electrode 202 can be positioned to accommodate differentdesigns of the body 50. For example, some humidification chambers may beshaped such that there are mechanical restrictions which prevent placingthe sensor electrode 202 on an exterior surface opposite the bridge 204.It may be desirable to move the sensor electrode 202 farther from thebase 52 as compared to the position of the bridge 204. This can increasethe change in capacitance relative to ground by increasing a distancebetween the ground (e.g, the base 52) and the sensor electrode 202.Because the capacitance of the sensor electrode 202 changes when liquidcontacts the bridge 204 even when the two are displaced from oneanother, the sensor electrode 202 can be vertically displaced from thebridge 204 (e.g., farther from the base 52 than the bridge 204). Thisallows the liquid level sensing system 222 to detect liquid levels belowthe position of the electrode sensor 202. Furthermore, the sensorelectrode 202 can be bigger than the bridge 204. This can allow foroverfill detection where there is a first discrete change in capacitancewhen the liquid level reaches the bridge 204 and a second discretechange in capacitance when the liquid level reaches the sensor electrode202. Thus, by sizing and positioning the sensor electrode 202 such thatthe second discrete change in capacitance occurs when the liquid levelnears the top of the chamber, the liquid level sensing system 222 can beconfigured to detect an overfill condition. The sensor electrode 202 canbe sized and positioned such that the second discrete change incapacitance can occur at when the liquid level reaches any desiredheight.

In some embodiments, the humidification chamber 46 includes containerswithin the body 50 for holding a liquid such that the liquid does notcontact the wall 53. Such containers can include, for example, tubes orother such structures within the body 50 of the humidification chamber46. The liquid level sensing system 222 can be configured to determineliquid levels in such a humidification chamber by positioning the bridge204 within the containers. The sensor electrode 202 can be positioned onthe exterior of the body 50, as before. Thus, when the liquid reachesthe bridge 204, there is a similar measurable change in capacitance ofthe system which can be detected by the liquid level sensing system 222.

FIG. 2A illustrates a block diagram of a liquid level sensing system 222incorporated with a controller 56 of a humidification unit 40. Theliquid level sensing system 222 can include a voltage source 302, adetection system 304, and liquid level sensors 200 configured to detecta change in capacitance of the liquid level sensing system 222corresponding to a liquid level condition, such as an out-of-liquidcondition or a chamber overfill condition. The controller 56 can controlthe voltage source 302 and receive signals from the detection system 304to determine the liquid level condition. The controller 56 can use theuser interface component to control the determination of the liquidlevel condition or to notify a user of the liquid level condition.

The controller 56 can include hardware, software, and/or firmwarecomponents used to control the humidification unit 40. The controller 56can be configured to control the voltage source 302, receive informationfrom the detection system 304, receive user input from the userinterface component 82, determine a level of liquid in a chamber 46, anddetermine a liquid level condition. The controller 56 can includemodules configured to control the attached components and analyzereceived information. The controller 56 can include data storage forstoring received information, control parameters, executable programs,and other such information.

The liquid level sensing system 222 includes a voltage source 302coupled to the liquid level sensors 200, particularly the electrodesensor 202 described with reference to FIGS. 2, 2B, and 2C. The voltagesource 302 can be a source of alternating current (“AC”) and varyingvoltage. The voltage source 302 can be electrically coupled to thesensor electrode 202.

The liquid level sensing system 222 includes a detection system 304coupled to the liquid level sensing sensors 200. The detection system304 can be configured to measure a change in capacitance in the liquidlevel sensors 200. For example, the detection system 304 can includeelectronic circuitry configured to produce a voltage across the sensorelectrode 202 which can be different from the supplied voltage from thevoltage source 302. The difference between the supplied voltage and thevoltage across the sensor electrode 202 can be related to thecapacitance of the system 222. The detection system 304 can include dataacquisition hardware configured to produce a signal corresponding to ameasured voltage, capacitance, resistance, or some combination of these.The detection system 304 can include measurement tools configured toacquire and/or display a value corresponding to a capacitance, voltage,resistance or the like.

The liquid level sensing system 222 can be coupled to the controller 56such that it can send information to and receive commands from thecontroller 56. For example, the liquid level sensing system 222 canreceive a command from the controller 56 to vary a voltage supplied bythe voltage source 302 to the sensor electrode 202. In some embodiments,the voltage source 302 produces a defined, known, or programmed voltagewithout input from the controller 56. The liquid level sensing system222 can send information from the detection system 304 to thecontroller. The controller 56 can receive this information and analyzeit to determine a liquid level condition. For example, the controller 56can receive information that indicates that the chamber is out of liquidor nearly out of liquid. The controller 56 can then generate anout-of-liquid alert, notification, or signal. Similarly, the controllercan receive information that indicates that the chamber has too muchliquid. The controller 56 can then generate an overfill alert,notification, or signal. In some embodiments, the detection system 304analyzes the information from the liquid level sensors 200 to determinethe liquid level conditions. In some embodiments, the controller 56receives information from the detection system 304 and can analyze thisinformation to determine a liquid level condition. In some embodiments,the liquid level sensing system 222 and/or the controller 56 can beconfigured to determine a volume of liquid present in the humidificationchamber 46 in addition to or instead of determining whether the chamberis out of liquid or has too much liquid. In some embodiments, thecontroller 56 can use the liquid level information as feedback incontrolling other systems such as the heater plate 54.

The user interface component 82 can be coupled to the controller 56 todisplay information and/or receive input from a user. The user interfacecomponent 82 can display, for example, information about the liquidlevel condition, a voltage supplied by the voltage source 302,measurements acquired by the detection system 304, results of analysisby the controller 56, or any combination of these. The user interfacecomponent 82 can be used to enter control parameters such as a voltageto supply to the sensor electrode 202, characteristics of the suppliedvoltage (e.g., frequency, amplitude, shape, etc.), a frequency ofmeasurements to be taken by the detection system 304, threshold valuesassociated with measurements from the detection system 304 for use indetermining out-of-liquid or overfill conditions, or any combination ofthese.

The controller 56 is configured to interact with the modules, datastorage, and external systems of the humidification unit 40. Thecontroller 56 can include one or more physical processors and can beused by any of the other components, such as the detection system 304,to process information. The controller 56 includes data storage. Datastorage can include physical memory configured to store digitalinformation and can be coupled to the other components of the humidifierunit 40, such as the liquid level sensing system and the user interfacecomponent 82.

FIG. 2B illustrates an example liquid level sensing system 222 in ahumidification chamber 46 with accompanying voltage source 302 anddetection system 304. The humidification chamber 46 can include anon-conducting wall 53 to which is attached the sensor electrode 202 onan exterior side of the wall 53 and a conducting bridge 204 on theinterior side of the wall 53. The humidification chamber includes a base52 sealed to the non-conducting wall 53. A base electrode 206 can beattached to the base 52 which can act as a virtual ground for the baseelectrode 206, or the base electrode 206 can be coupled to groundthrough some other means. The voltage source 302 can supply a voltagewhich varies in current, voltage, or both to the sensor electrode 202.The detection system 304 can be coupled to the sensor electrode 202 andthe base electrode to measure changes in capacitance. By determining achange in capacitance, the detection system can determine a liquid levelcondition in the humidification chamber 46.

When a conductive liquid in the humidification chamber 46 reaches thebridge 204, the bridge 204 is conductively coupled to the base electrode206. This creates a virtual short to ground from the bridge 204, throughthe liquid, and to the ground. The bridge 204 is also capacitivelycoupled to the sensor electrode 202. Creating a virtual short from thebridge 204 to the base electrode 206 can change the capacitance of thesystem which can be measured as a discrete increase in capacitance ofthe sensor electrode 202 relative to ground. The liquid level sensingsystem 222 can detect this discrete increase in capacitance anddetermine a corresponding liquid level condition, as described morefully herein.

When a non-conductive liquid in the humidification chamber 46 reachesthe bridge 204, the non-conductive liquid can act as a dielectric in acapacitive system. The bridge 204 in this scenario is capacitivelycoupled both to the sensor electrode 202 and to the base electrode 206.The presence of the non-conductive liquid at the bridge 204 causes adiscrete change in the capacitance of the system which can be detectedby measuring the capacitance of the sensor electrode 202 relative toground. The liquid level sensing system 222 can detect this change incapacitance and determine a corresponding liquid level condition, asdescribed more fully herein.

As illustrated in FIG. 2B, the sensor electrode 202 can be verticallyoffset relative to the bridge 204. As a result, the liquid level sensingsystem 222 can experience two discrete changes in capacitance. A firstchange occurs when the liquid reaches the bridge 204. A second changeoccurs when the liquid reaches the sensor electrode 202. The detectionsystem can be configured to detect the two discrete changes anddetermine a corresponding liquid level condition. For example, thesecond discrete change can correspond to the chamber 46 having too muchliquid, or an overfill condition.

In some embodiments, the sensor electrode 202 can be larger than thebridge 204. The increase in size can result in an increase incapacitance as capacitance is generally correlated to a physical size ofan object. This increase in capacitance can increase the sensitivity ofthe system to changes in liquid levels. In some embodiments, theincrease in size of the sensor electrode 202 can be used to detect anoverfill condition due at least in part to a change in capacitance whenliquid levels rise above the bridge 204. For example, the sensorelectrode 202 and the bridge 204 can be positioned opposite one another.Because the sensor electrode 202 is larger than the bridge 204, it canextend vertically beyond the bridge 204. As a result, when the liquidlevel reaches the bridge 204 there will be a first discrete change incapacitance and when the liquid level is over the top of the bridge 204there will be a second discrete change in capacitance as the liquidlevel will be of a height with the top of the sensor electrode 202.These changes in capacitance can be used to detect various liquid levelconditions including an out-of-liquid condition or an overfillcondition.

In some embodiments, the detection system 304 is configured to detectany change in capacitance in the liquid level sensing system 222. Thedetection system 304 can be configured to correlate these changes withvolumes of liquid in the chamber 46. For example, as liquid levelsincrease, the capacitance of the sensor electrode 202 can change inrelation to the level changes. The detection system 304 can determine anapproximate liquid level value corresponding to a value of thecapacitance. In this way, the liquid level sensing system 222 canestimate the water level in the humidification chamber 46.

FIG. 2C illustrates an example liquid level sensing system 222 in ahumidification chamber 46 having a wicking material 502 along aninterior of a non-conducting wall 53. The wicking material 502 isconfigured to provide a means for a liquid to move up the materialthrough capillary action when there is any liquid in the chamber 46.This allows the liquid level sensing system 222 to detect a presence ofa liquid in the chamber 46.

When the chamber 46 receives any conductive liquid, the conductiveliquid will ascend the wicking material through capillary action. Oncethe conductive liquid arrives at a height that is level with the sensorelectrode 202, the capacitance of the sensor electrode 202 changes asthe conductive liquid is grounded due at least in part to the conductiveconnection with the base 52. The detection system 304 can detect thischange in capacitance and signal the presence of liquid in the chamber46. This can be used to determine whether there is liquid in the chamber46 or if there is an out-of-liquid condition.

FIG. 2D illustrates a flow chart of an example method 600 of detectingliquid levels in a humidification chamber 46 based at least in part ondetermining a change in capacitance of a sensor electrode 202. Theexample method 600 as described herein provides several advantageousfeatures. One such feature is that the example method 600 can be used ina system where the humidification chamber 46 contains a conductive ornon-conductive liquid without changing the manner in which the methodfunctions. For example, determining a liquid level based at least inpart on a change in capacitance between the sensor electrode 202 andground works when the chamber 46 contains either conducting ornon-conducting liquids, as described herein. For ease of description,the method will be described as being performed by the liquid levelsensing system 222, but any individual step or combination of steps canbe performed by any component of the liquid level sensing system 222 orthe controller 56 of the humidification unit 40.

In block 605, the liquid level sensing system 222 uses a voltage source302 to produce a varying electrical output that is coupled to a sensorelectrode 202 attached to an exterior surface of a non-conducting wall53 of a body 50 of the humidification chamber 46. The voltage source 302can produce an electrical signal that varies in current, voltage, orboth. For example, the voltage source 302 can be an AC voltage source.In some embodiments, the voltage source 302 is controlled by thecontroller 56. In some embodiments, the voltage source 302 isindependently controlled or produces a selected, known, defined, orpre-determined electrical output.

In block 610, the liquid level sensing system 222 determines acapacitance of the sensor electrode 202 relative to ground. A detectionsystem 304 can measure parameters of the liquid level sensing system 222such as, for example, capacitance, resistance, voltage, or anycombination of these. The detection system 304 can use this informationto detect a change in the capacitance of the system 222.

The detection system 304 can include circuitry configured to producemeasurable differences in parameters in response to a change incapacitance of the sensor electrode 202. For example, the detectionsystem 304 can include circuit having a voltage divider having aresistor in series with the sensor electrode 202. The voltage source 302can provide an AC voltage to the circuit. The detection system 304 canmeasure the voltage across the resistor and the sensor electrode 202.The capacitance of the sensor electrode 202 can be calculated based atleast in part on the values of the measured voltages. As anotherexample, the detection system 304 can include a circuit having a knowncapacitor in series with the sensor electrode 202. The voltage sourcecan provide an AC voltage to the circuit. The detection system 304 canmeasure the voltage across the known capacitor and the sensor electrode202 and calculate the capacitance of the sensor electrode 202. Otherknown methods of determining capacitance can be used by the detectionsystem 304.

In some embodiments, the chamber 46 can be configured to hold conductiveliquid. The sensor electrode 202 can be capacitively coupled to thebridge 204 and the bridge 204 can be conductively coupled to the baseelectrode 206, which is grounded. The conductive liquid turns the bridge204 into a ground thereby creating a capacitance between the sensorelectrode 202 and ground through the bridge 204. In some embodiments,the chamber 46 can be configured to hold non-conductive liquid. Thesensor electrode 202 can be capacitively coupled to the bridge 204 andthe bridge 204 can be capacitively coupled to the base electrode 206,which is grounded. This system creates a capacitive system having adielectric that affects the capacitance between the sensor electrode 202and the bridge 204, and between the bridge 204 and the base electrode206, which is grounded. In some embodiments, the chamber 46 includes awicking material on an interior surface of the non-conducting wall 53.The chamber 46 is configured to hold conductive liquid which moves upthe wicking material when placed in the chamber 46. When the conductivematerial reaches the sensor electrode 202, the conducting liquid acts tochange the capacitance of the sensor electrode 202 where the sensorelectrode 202 is capacitively coupled to the conducting liquid in thewicking material, which is grounded.

In block 615, the liquid level sensing system 222 determines a liquidlevel based at least in part on the capacitance determined in block 610.According to the several embodiments described herein, the liquid levelsensing system 222 can determine a volume of liquid in the chamberand/or it can determine a liquid level condition such as anout-of-liquid condition or an overfill condition.

In block 620, the liquid level sensing system 222 can create anotification related to the liquid level determined in block 615. Forexample, if an out-of-liquid condition is determined, the liquid levelsensing system 222 can produce an audible or visible alert to a user orsend a signal to the controller 56 of the humidification unit 40. Thecontroller 56 can change control parameters based at least in part onthe received notification regarding the liquid level, such as ceasing toenergize a heater plate 54. The liquid level sensing system 222 caninclude its own notification system or use the user interface component82 to notify operators or users of liquid level conditions.

Examples of liquid level sensing systems and associated components andmethods have been described with reference to the figures. The figuresshow various systems and modules and connections between them. Thevarious modules and systems can be combined in various configurationsand connections between the various modules and systems can representphysical or logical links. The representations in the figures have beenpresented to clearly illustrate principles related to sensing liquidlevels using capacitive and conductive techniques, and details regardingdivisions of modules or systems have been provided for ease ofdescription rather than attempting to delineate separate physicalembodiments. The examples and figures are intended to illustrate and notto limit the scope of the inventions described herein. For example, theprinciples herein may be applied to a respiratory humidifier as well asother types of humidification systems, including surgical humidifiers.The principles herein may be applied in respiratory applications as wellas in other scenarios where liquid level sensing is desirable.

As used herein, the term “processor” refers broadly to any suitabledevice, logical block, module, circuit, or combination of elements forexecuting instructions. For example, the controller 56 can include anyconventional general purpose single- or multi-chip microprocessor suchas a Pentium® processor, a MIPS® processor, a Power PC® processor, AMD®processor, or an ALPHA® processor. In addition, the controller 56 caninclude any conventional special purpose microprocessor such as adigital signal processor. The various illustrative logical blocks,modules, and circuits described in connection with the embodimentsdisclosed herein can be implemented or performed with a general purposeprocessor, a digital signal processor (DSP), an application specificintegrated circuit (ASIC), a field programmable gate array (FPGA), orother programmable logic device, discrete gate or transistor logic,discrete hardware components, or any combination thereof designed toperform the functions described herein. Controller 56 can be implementedas a combination of computing devices, e.g., a combination of a DSP anda microprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration.

Data storage can refer to electronic circuitry that allows information,typically computer or digital data, to be stored and retrieved. Datastorage can refer to external devices or systems, for example, diskdrives or solid state drives. Data storage can also refer to fastsemiconductor storage (chips), for example, Random Access Memory (RAM)or various forms of Read Only Memory (ROM), which are directly connectedto the communication bus or the controller 56. Other types of memoryinclude bubble memory and core memory. Data storage can be physicalhardware configured to store information in a non-transitory medium.

Flow and Temperature Sensing System

With reference to FIG. 1, the controller 56 also receives input from aflow sensor 84 and at least one temperature sensor 86. Any suitable flowsensor 84 can be used and any suitable temperature sensor 86 can beused. In some configurations, the flow sensor 84 can include atemperature sensor 86.

Preferably, the flow sensor 84 is positioned between ambient air and thehumidification chamber 46. More preferably, the flow sensor 84 ispositioned between the pressurized gas source 30 and the humidificationchamber 46. In the illustrated configurations, the flow sensor 84 ispositioned on the inlet port 60 of the humidification chamber 46. Insome configurations, the sensor 84 can be positioned on a connector usedto couple a conduit to the inlet port 60. The sensor 84 also can bepositioned in any suitable location.

Preferably, the temperature sensor 86 is positioned between thehumidification chamber 46 and the user. More preferably, the temperaturesensor 86 is positioned between the humidification chamber 46 and theinterface 74. In the illustrated configurations, the temperature sensor86 is positioned on the outlet port 62 of the humidification chamber 46.In some configurations, the sensor 86 can be positioned on a connectorused to couple a conduit to the outlet port 62. The sensor 86 also canbe positioned in any suitable location.

At least a portion of one or more of the sensors 84, 86 can be mountedoutside of a flow path defined through the humidification system 20. Insome configurations, one or more of the sensors 84, 86 is configured forremoval from the flow path without directly accessing the flow paththrough the humidification system 20. Preferably, the one or moresensors 84, 86 is configured to sense one or more characteristic of flowthrough a portion of the flow path through the humidification systemwhile remaining pneumatically sealed from the flow path.

With reference to FIG. 2, in the illustrated configuration, the inletport 60 comprises an aperture 90. The aperture 90 extends through a wallof the inlet port 60 and provides a communication path through the wallof the inlet port 60. Similarly, in the illustrated configuration, theoutlet port 62 comprises an aperture 92. The aperture 92 extends througha wall of the outlet port 62 and provides a communication path throughthe wall of the outlet port 62. In some configurations, the aperture 90and the aperture 92 each is defined around a cylinder with an axis andthe axes extend generally parallel with each other. Other configurationsare possible. In addition, while the illustrated configurations positionthe apertures 90, 92 within portions of the humidification chamber 46,one or more of the apertures can be positioned in other locations on thehumidification system 20.

With reference now to FIG. 3, the humidification chamber 46 is shownwith a first seal 100 positioned within the aperture 90 in the inletport 60 and a second seal 102 positioned within the aperture 92 in theoutlet port 62. The first seal 100 preferably pneumatically seals theaperture 90 and the second seal 102 preferably pneumatically seals theaperture 92 such that the gas path defined within the respectiveportions of the humidification system 20 is isolated from ambient by theseals 100, 102. In other words, the seals 100, 102 substantially closethe apertures 90, 92. Accordingly, in the illustrated configuration, theseals 100, 102 define a barrier that reduces the likelihood of fluid orgas passing through the apertures 90, 92. In some applications, at leastone of the seals 100, 102, and preferably both of the seals 100, 102,also is resistant to the passage of water vapor.

The first seal 100 and the second seal 102 can be formed from anysuitable material. In some applications, the first seal 100 and thesecond seal 102 are formed from a resilient or flexible material.Preferably, at least one of the seals 100, 102 is formed entirely of aresilient or flexible material. In some applications, at least a portionof at least one of the seals 100, 102 is formed entirely of a resilientor flexible material. In some applications, one or more of the seals100, 102 can be formed of a material with a Shore-A hardness of betweenabout 20 and about 60, and more preferably between about 30 and about40. In some applications, one or more of the seals 100, 102 can beformed of Silicone, polyethylene, or thermoplastic polyurethane.

In some applications, such as that shown in FIG. 17, at least a portionof at least one of the seals 100, 102 can be formed with a rigidmaterial. For example but without limitation, at least a portion of atleast one of the seals 100, 102 can be formed of a metal. When at leastone of the seals 100, 102 is formed entirely of a rigid material, theseal preferably is configured to provide repeatable contact and thermalconduction between the barrier formed by the seal 100, 102 and anassociated sensor. In some embodiments, the seals 100, 102 can be formedof the same material as the chamber 46, can be formed of a differentmaterial with a different (preferably higher) thermal conductivity, or acombination thereof. If a combination is used, preferably at least aportion of a tip 101, or at least a portion exposed to flow within theport, and in some configurations, the ultimate end of the tip 101, ofthe seal is formed of a material with a higher thermal conductivity(e.g., aluminum, copper). In some configurations, the tip 101 ispositioned such that the seal 100, 102 extends to an axial center of theport. In some configurations, the tip 101 is positioned such that theseal 100, 102 traverses at least half of the transverse dimension of theport 60, 62. The seals 100, 102 can be formed integrally with thechamber 46 or, for example but without limitation, can be overmoulded,press-fit and glued, co-moulded, or welded thereto.

In some embodiments, at least one of the seals 100, 102 can be formed ofa first, more thermally-conductive portion arranged to receive an end ora sensing portion of the associated sensor 130, 132 and a second, lessthermally-conductive or thermally non-conductive portion. The secondportion preferably is arranged to reduce or eliminate a conduction orother transmission of heat from the sensing element or tip of the sensor130, 132 into the surrounding portions of the apparatus. For example,where the associated sensor 130, 132 comprises a thermistor, the secondportion preferably generally or substantially thermally isolates thethermistor. In other words, the tip of the thermistor could be arrangedin the more thermally-conductive first portion, which can be positionedwithin the flow of gases that the thermistor is measuring. In someconfigurations, the less thermally-conductive or thermallynon-conductive portion may comprise a different material from the morethermally-conductive portion. In some configurations, a porous materialor a foam material can be used in provide improved insulation. In suchan arrangement, less heat is conducted from the first portion to theambient environment through the second portion. The reduced conductionallows the thermistor to provide a more accurate reading of the gas bymaximizing or increasing the heat transfer between the first portion andthe tip of the thermistor.

In some embodiments, means may be provided to increase a reliability ofa contact between the associated sensor and the tip portion of the seal.For example, in the arrangement of FIG. 17, a spring, or any othersuitable biasing or cushioning member, may be interposed between asensor 130, 132 and a cartridge 160 that carries or otherwise supportsthe sensor 130, 132. In such arrangements, the member 103 (e.g., spring,biasing member or cushioning member) compressed to provide a relativelyrepeatable force between the end of the sensor 130, 132 and the tip 101,for example but without limitation. In some applications, a flexible orelastic membrane can connect the tip 101 to the chamber 46. In suchconfigurations, the tip 101 can be displaceable relative to at leastsome portion of the chamber 46 (including the port 60, 62). In otherwords, the flexible or elastic membrane can stretch with the insertionof the sensor 130, 132 due to contact of the sensor 130, 132 with thetip 101 to provide a generally repeatable force between the end of thesensor 130, 132 and the tip 101 while providing a generally contactingthermal mass at the tip 101.

In some arrangements, at least one of the seals 100, 102, and preferablyboth, comprises a feature to retain the seal 100, 102 in position withinthe respective aperture 90, 92. With reference to FIG. 4, theillustrated first seal 100 comprises an outer flange 104 and an innerflange 106. As shown in FIG. 5, a channel 108 is defined between theouter flange 104 and the inner flange 106. The channel 108 preferably issized to accommodate a wall 110 of the inlet port 60. More preferably,the channel 108 is sized to form a fluid and/or gas tight seal with thewall 110 that surrounds the aperture 90. In the configurationillustrated in FIGS. 3-9, a base surface of the channel 108 has asurface that is at least partially curved or sloping to improve the sealbetween the seal 100 and the wall defining the aperture 90. In someconfigurations, such as that shown in FIGS. 18A-18G, the base surfacecan be substantially planar instead of at least partially curved orsloping.

In some arrangements, at least one of the seals 100, 102 can bepermanently or at least semi-permanently attached to the apertures 90,92. In some arrangements, at least one of the seals 100, 102 can beremovable and replaceable. The seals 100, 102 can be configured to havea useable life similar to that of one of the other components. Forexample, the seals 100, 102 preferably comprise a useable life similarto the chamber 46 such that the chamber 46 and the seals 100, 102 wouldbe disposed of at the same time. In some configurations, especiallywhere the seals 100, 102 are permanently attached to the chamber 46, theseals 100, 102 preferably have a longer life than the chamber 46 suchthat the seals 100, 102 are not the limiting component on a life span ofthe chamber 46.

In the illustrated configuration, the inner flange 106 has a smallerouter circumference than the outer flange 104. The smaller outercircumference of the inner flange 106 facilitates insertion of the seal100 into the aperture 90. The inner flange 106 of the first seal 100 cancomprise a sloped surface 112 to further assist with the installation ofthe first seal 100 into the aperture 90. While it is possible to slopeor taper a surface of the outer flange 104 to facilitate installation,because the illustrated first seal 100 is designed to be pressed intothe aperture 90 from the outside of the inlet port 60, the sloped ortapered surface 112 preferably is positioned on the inner flange 106.

With reference to FIG. 10, the illustrated second seal 102, similar tothe first seal 100, comprises an outer flange 114 and an inner flange116. As best shown in FIG. 12, a channel 118 is defined between theouter flange 114 and the inner flange 116. As shown in FIG. 10, thechannel 118 preferably is sized to accommodate a wall 120 of the outletport 62. More preferably, the channel 118 is sized to form a fluidand/or gas tight seal with the portion of the wall 120 that generallysurrounds the aperture. As with the seal 100, a base surface of thechannel 118 has a surface that is at least partially curved or slopingto improve the seal between the seal 102 and the wall defining theaperture 92. In some configurations, the base surface can besubstantially planar (see, e.g., FIGS. 18A-18G).

The inner flange 116 has a smaller outer circumference than the outerflange 104. The smaller outer circumference of the inner flange 116facilitates insertion of the seal 102 into the aperture 92. The innerflange 116 of the second seal 102 can comprise a curved surface 122 toassist with the installation of the second seal 102 into the aperture92. As with the first seal 100, it is possible to slope or taper asurface of the outer flange 114 to facilitate insertion but, because theillustrated second seal is designed to be pressed into the aperture 92from the outside of the outlet port 62, the sloped or tapered surfacepreferably is positioned on the inner flange 116.

With reference to FIG. 16, a first sensor 130 is insertable into thefirst seal 100 and a second sensor 132 is insertable into the secondseal 102. In some configurations, the sensors 130, 132 will not seal theapertures if the seals 100, 102 are not positioned within the apertures.The first seal 100 and the second seal 102 define a barrier that ispositioned between the gas flow path and the first sensor 130 and thesecond sensor 132 respectively. With the first seal 100 and the secondseal 102 defining the barrier, the sensors 130, 132 remain external tothe flow path. Because the first and second sensors 130, 132 remainexternal to the flow path, the sensors 130, 132 can be reused and neednot be cleaned before subsequent reuse. Even though the sensors 130, 132remain external to the flow path, however, the sensors 130, 132 are ableto provide measurements of flow characteristics. For instance, the firstsensor 130 can be used to detect flow rate while the second sensor canbe used to detect temperature.

Any suitable components can be used as the sensors. For example,thermocouples, resistance temperature detectors, fixed resistors and thelike can be used as the sensors 130, 132. In the illustratedarrangement, the sensors 130, 132 comprise thermistors. The secondsensor 132 uses a single thermistor 134 mounted to a body 136. Thesensor 132 can be used to sense a temperature of the flow in the flowpath. As shown in the illustrated arrangement, the temperature sensor132 can be positioned to extend the thermistor 134 into the flow path onthe outlet port 62. In some configurations, the temperature sensor canbe positioned in other regions of the humidification system 20 (e.g., onthe conduit 44, the conduit 70, or the like).

The illustrated first sensor 130 preferably comprises a first thermistor140 and a second thermistor 142 mounted on a single body 144. In someconfigurations, the first thermistor 140 and the second thermistor 142can be mounted on separate bodies; however, mounting the first andsecond thermistors 140, 142 on the single body 144 improves the accuracyin positioning of the first and second thermistors 140, 142 relative toeach other. As shown in the illustrated arrangement, the first sensor130 can be positioned to extend the two thermistors 140, 142 into theflow path on the inlet port 60. Positioning the first sensor 130 on theinlet is desired because the sensor is detecting flow rate andpositioning the first sensor 130 in an region of relatively dry flow isdesirable. In some configurations, the flow sensor 130 can be positionedin other regions of the humidification system 20 (e.g. on the conduit44, the conduit 70, or the like).

Through the use of the first and second thermistors 140, 142, a constanttemperature flow measurement approach can be used. In this approach, thefirst thermistor 140 functions as a reference sensor that measures theflow temperature at the sensing location and the second thermistor 142,which can be a heated thermistor, is heated to a preset temperaturedifferential above the flow temperature. In some applications, aresistor can be used to heat the second thermistor 142 instead of usinga heated thermistor. In some configurations, all of the thermistors canbe both heated and non-heated thermistors. Flow velocity can bedetermined using the measured flow temperature, the known heat transfercharacteristics of the heated second thermistor 142 and the powerconsumed to maintain the temperature difference between the twothermistors 140, 142. In other words, the power required to maintain thesecond thermistor 142 at the elevated temperature is processed todetermine the flow rate. Thus, the first sensor 130 and the secondsensor 132 preferably measure flow velocity within about 50% of theactual point velocity and temperature within about 0.3 degrees C. Othertechniques also can be used. For example but without limitation,constant power can be provided to the thermistors and the heat conductedinto a nearby thermistor can be used to determine the rate of flow.

As illustrated in FIG. 16, the first sensor 130 can be inserted into thefirst seal 100 and the second sensor 132 can be inserted into the secondseal 102. The seals 100, 102 isolate the sensors 130, 132 from the flowsuch that the sensors 130, 132 are protected against contamination fromthe flow. As such, the sensors 130, 132 need not be cleaned and can bereused without cleaning.

With reference to FIGS. 4 and 10, one or more of the seals 100, 102 candecrease in thickness toward a respective distal end 124, 126. Withparticular reference to FIG. 4, the seal 100 has a first thickness t1that is larger than a thickness t2 present at the distal end 124 of theseal 100. Preferably, a portion of the seal 100 that is adapted to be incontact with the sensing portion of the first sensor 130 has the reducedthickness t2 to improve sensitivity while improving robustness with thethicker portion. In some configurations, the portion of the seal 100that is adapted to contact the sensing portion of the first sensor has asubstantially constant thickness to improve performance. With referenceto FIG. 10, the seal 102 is constructed similarly to the seal 100 with afirst thickness t3 being larger than a second thickness t4. Othersuitable configurations are possible. In some configurations, the sensor130, 132 is inserted at such a depth into the seal 100, 102 that the tipof the seal 100, 102 will be stretched by the insertion. In someconfigurations, the tip of the seal 100, 102 will stretch before otherregions of the seal 100, 102. The stretching of the tip can decrease thethickness of the seal 100, 102 towards the distal end when compared tothe seal 100, 102 without the sensor 130, 132 inserted. The stretchingof the tip also decreases the likelihood of an air bubble formingbetween the tip of the sensor 130, 132 and the tip of the seal 100, 102,which air bubble could reduce the thermal conduction between the seal100, 102 and the sensor 130, 132.

With continued reference to FIGS. 4 and 10, the distal ends 124, 126 ofthe illustrated seals 100, 102 have a decreased diameter. In theillustrated configuration, the distal ends 124, 126 are necked downrelative to the other end. In some configurations, a smooth taper orother suitable configuration can be used.

In the illustrated configuration, the first sensor 130 comprises thefirst and second thermistors 140, 142 on the single body 144. The firstsensor 130 is received within the first seal 100. Desirably, thermalconduction is minimized between the first thermistor 140 (i.e., thereference temperature) and the second thermistor 142 (i.e., the heatedthermistor for flow measurement). Heat conduction between thethermistors 140, 142 within single barrier has been discovered. The heatconduction can result in a circular reference: with flow temperaturemeasured using the non-heated first thermistor 140, a constanttemperature offset (e.g., approximately 60 degrees C.) is applied to theheated second thermistor 142 and the power required to achieve thistemperature offset is measured; if the heated second thermistor 142heats the non-heated first thermistor 140, the target temperature raisesand the cycle repeats. Thus, the illustrated first seal 100 comprisestwo separate sleeves 146, 148 for the two thermistors 140, 142. Bypositioning the first thermistor 140 in the first sleeve 146 and thesecond thermistor 142 in the second sleeve 148, the first thermistor 140and the second thermistor 142 are substantially isolated and the seal100 provides independent barrier layers for each thermistor 140, 142. Insome configurations, the first thermistor 140 and the second thermistor142 may be substantially isolated by using baffles between thethermistors 140, 142, providing different orientations of thethermistors 140, 142, and/or using flow sensors, for example but withoutlimitation.

An alternative seal configuration is shown in FIGS. 19A-19C. In theillustrated embodiment, the seal 102 includes a generally cylindricalbase 115. The seal 102 also comprises a generally bell-shaped head 117.The illustrated bell-shaped head 117 comprises a plurality of triangularribs 119 around its perimeter. In some embodiments, a channel 118 can bedefined between the base 115 and the head 117 and sized to accommodatethe wall 120 of the outlet port 62. The ribs 119 can deflect to allowthe seal 102 to be inserted into the aperture 92 then return to anexpanded state to help hold the seal 102 in place within the aperture92. As the ribs 119 depress, they spread into spaces 121 between theribs 119. In some embodiments, a radio of a width of the rib 119 to awidth of the space 121 between ribs 119 is about 1:1. In someembodiments, the ratio is about 3:7. A ratio that is too high (i.e., thespace 121 between ribs 119 is small compared to the ribs 119) may notallow the ribs 119 to depress sufficiently, resulting in greaterdifficulty installing the seal 102 in the aperture 92. A ratio that istoo low (i.e., the space 121 is large compared to the ribs 119) mayprovide a reduced retention force so that the seal 102 is not held assecurely in the aperture 92. In the illustrated embodiment, the sealincludes eight ribs 119, but more or fewer ribs 119 are also possible.However, if too many ribs 119 are included, the ribs 119 would be madethinner and might be weaker. Alternatively, including too few ribs 119might require making the ribs 119 larger, leaving less space to spread.

When the sensor 132 is inserted into the seal 102 of FIGS. 19A-19C, atip 123 of the seal 102 can stretch to conform to the shape of thesensor 132. As the amount of stretch to accommodate the sensor 132increases, the seal material becomes thinner. This can advantageouslyimprove the reactivity and accuracy of the sensor, increase the contactarea between the sensor as seal as the seal stretches to match the shapeof the sensor, and more securely hold the seal in the aperture 92.However, if the tip 123 of the seal is too flat and requires too great adegree of stretch to accommodate the sensor, it can be more difficult toinsert the sensor in the seal and the seal material may degrade orbreak. In the illustrated embodiment, the seal can have a length ofabout 7.50 mm, a base 115 diameter of about 7 mm, a diameter measured atthe widest portion of the ribs 119 of about 6.50 mm, and a tip 123thickness of about 0.020 mm. Alternative configurations of seals havingribs 119 are shown in FIGS. 20A-20C. The seals of FIGS. 20A and 20B canboth have lengths of about 6 mm, base 115 diameters of about 8 mm,diameters measured at the widest portion of the ribs 119 of about 7.50mm, and tip thicknesses of about 0.20 mm. However, the seal of FIG. 20Acan have ribs 119 sized so that the space 121 between ribs is about 1.4mm, whereas the seal of FIG. 20B can have ribs 119 sized so that thespace 121 is about 1.1 mm. The seal of FIG. 20C can have a length ofabout 4.50 mm, a base diameter of about 8 mm, a diameter measured at thewidest portion of the ribs 119 of about 7.50 mm, and a tip thickness ofabout 0.20 mm. The ribs 119 of the seal of FIG. 20C can have slightlyrounded or curved ends.

With reference again to FIG. 16, the sensors 130, 132, because they areremovable and replaceable, preferably have a repeatable tip thermalmass. In some arrangements, the accuracy of the sensors 130, 132 can beimproved if the thermal mass exposed inside of the flow passage isrepeatable. For this reason, the depth of insertion of the sensors 130,132 into the respective flow preferably is generally repeatable.

To provide repeatable depth of insertion of the sensors 130, 132, and tosimplify the mounting of the sensors 130, 132, the illustratedconfiguration comprises a cartridge 160. With reference to FIG. 3 andFIG. 21, the cartridge 160 and the top of the illustrated humidificationchamber 46 comprise a coupling configuration. In the illustratedconfiguration, the top of the humidification chamber 46 comprises arecess structure 162 while the cartridge 160 comprises a correspondingboss structure 164. In some configurations, the top of thehumidification chamber can comprise at least a portion of a bossstructure while the bottom of the cartridge 160 comprises at least aportion of a corresponding recess structure. Another configuration isshown in FIG. 36, wherein an upwardly protruding member 165 ispositioned on the top of the chamber 46 and a corresponding recess 167is formed on the cartridge 160. In the configuration shown in FIG. 36,the cooperation of the protruding member 165 and the recess 167 canguide the connection between the cartridge 160 and the chamber 46. Anyother suitable configuration can be used.

The sensor 130, 132 can include a shield configured to protect at leasta tip or sensing component of the sensor 130, 132 from damage that mightbe caused by incidental or inadvertent contact, bumping or knocking, forexample but without limitation. In some configurations, the shield caninclude one or more fingers 131 arranged around the tip or sensingelement of the sensor 130, 132. In some configurations, one or more ofthe fingers can be curved such that a portion of the finger is locatedsubstantially above the tip or sensing element of the sensor 130, 132and another portion of the finger is located substantially alongside ofthe tip or sensing element of the sensor 130, 132.

In the illustrated configuration shown in FIG. 3, a ridge 166 defines atleast a portion of the recess structure 162. The ridge 166 extendsupward from an upper surface 170. The ridge defines a stop 172 and apair of snap recesses 174. As shown in FIG. 21, a pair of protrusions180 extend downward from a lower surface 182 of the illustratedcartridge 160. Each of the protrusions 180 comprises a locking tab 184.Each locking tab 184 is at an end of a respective arm 186 in theillustrated configuration. The locking tabs 184 can deflect inward whilethe cartridge 160 is being slid into position on the chamber 46. Thelocking tabs 184 snap into position within the snap recesses 174 formedon the ridge 166. With the locking tabs 184 snapped into position withinthe snap recesses 174, the cartridge 160 is secured in position in thesliding direction. In addition, a stop 190 on the cartridge 160 movesinto proximity with or contacts the stop 172 of the ridge 162. Becausethe sensors 130, 132 are slid into position within the ports 60, 62, thecartridge 160 also is generally secured against movement normal to thesliding direction.

In some configurations, such as that shown in FIG. 36, the cartridge 160includes one or more arms 191. The arms 191 can be adapted to extendalong outer sides of the ports 60, 62 of the chamber 46. The arms canassist with locating the cartridge 160 correctly with respect to thechamber 46. In addition, if the installed cartridge 160 is bumped orknocked, the force from the bump or knock can be transmitted to the oneor more arms 191 and away from the more fragile sensors 130, 132.

In the illustrated configuration, the arms 191 comprise an interlockportion 195 while the chamber 46 comprises an interlock portion 197. Insome configurations, the interlock portion 197 of the chamber ispositioned laterally outward from the ports 60, 62. The lateraldisplacement provides for a stable connection. The interlock portion 197can be positioned on bosses 199 or the like. In some configurations,gripping portions 193 can be defined in an outer surface or along anouter surface of the chamber 46. In one configuration, the grippingportion 193 can be defined on one side of the interlock portion 197 orboss 199 while the majority of the cartridge 160 will be positioned onanother side of the interlock portion 197.

Any suitable shape can be used for the interlock portions 195, 197. Inthe illustrated configuration, the interlock portion 197 of the chamber46 comprises a bump that extends upward while the interlock portion 195of the chamber comprises a recess that corresponds to bump of theinterlock portion 197. Preferably, when the chamber 46 and the cartridge160 are fully mated, the two interlock portions 195, 197 hold thechamber 46 and the cartridge 160 together with at least a slight forcethat must be overcome for separation of the chamber 46 from thecartridge 160.

The cartridge 160 defines a chassis that carries the sensors 130, 132and other desired electrical components. In the illustratedconfiguration, the cartridge comprises wings 192 that define sockets andthe sensors 130, 132 plug into the sockets, as shown in FIG. 21. In someconfigurations, the sensors 130, 132 are designed for removal andreplacement with the same cartridge 160. In some configurations, thecartridge 160 is designed for limited time use and will be disposedwithout allowing the sensors 130, 132 to be removed and replaced. Insome configurations, the portions of the cartridge 160 carrying thesensors 130, 132 are separable from the central portion of the cartridge160, which generally houses electronics or the like. Such configurationsenable replacement of the sensors 130, 132 without replacing the portionof the cartridge 160 that contains the main portion of the housedelectronics.

With reference to FIG. 22, the cartridge comprises a recessed electricalconnector 161. The electrical connector 161 is electrically connected tothe sensors 130, 132 in any suitable manner. Preferably, the electricalconnector 161 is a female USB connector. In addition, the electricalconnector 161 is adapted to provide an electrical connection to thecontroller 56 or any other suitable component. Preferably, with thecartridge 160 mounted to the humidification chamber 46, when thehumidification chamber 46 is installed into the humidification unit 40,a corresponding connector 307 (preferably, a male USB connector or thelike) on the humidification unit 40 makes electrical connection with theconnector 161. In this manner, connection of the sensors to thecontroller 56 is greatly simplified and the possibility of improperelectrical connection is greatly reduced.

The wings 192 on the illustrated chassis provide mounting structures forthe sensors 130, 132 and also position the sensors 130, 132 forrepeatable depth of insertion of the sensing portions of the sensors130, 132 into the flow path. Advantageously, when the sensors 130, 132are mounted in the cartridge 160 and that cartridge 160 is snapped intoposition on the chamber 46, the sensing portions of the sensors 130, 132are positioned in a desired location within the flow path.

Composite Tubes

As described above, the respiratory humidification system 20 can includea conduit 44 connecting the gas source 30 to the humidification unit 40,an inspiratory conduit 70, and/or an expiratory conduit. In someembodiments, portions or entireties of any or all of these conduits canbe composite tubes, which can be tubes having two or more portions orcomponents. Composite tubes as described herein can also be used otherapplications, for example but without limitation, in laparoscopicsurgery. For example, the use of a composite tube as the conduit 713 inthe example insufflation system 701 illustrated in FIG. 1B can helpdeliver humidified gases to the patient 705 surgical site with minimizedheat loss. This can advantageously reduce overall energy consumption inthe insufflation system, because less heat input is needed to compensatefor heat loss

With reference to FIG. 37A, an example composite tube comprises a firstelongate member 203 and a second elongate member 205. In the illustratedembodiment, the first 203 and second 205 elongate members are distinctcomponents; however, in other embodiments, the first and second elongatemembers can be regions of a tube formed from a single material. Thus,the first elongate member 203 can represent a hollow portion of a tube,while the second elongate member 205 represents a structural supportingor reinforcement portion of the tube which adds structural support tothe hollow portion. The hollow portion and the structural supportingportion can have a spiral configuration, as described herein. Thecomposite tube 201 may be used to form the inspiratory conduit 70 and/orthe expiratory conduit as described above, a coaxial tube, or any othermedical tube.

In this example, the first elongate member 203 comprises a hollow bodyspirally wound to form, at least in part, an elongate tube having alongitudinal axis LA-LA and a lumen 207 extending along the longitudinalaxis LA-LA. In at least one embodiment, the first elongate member 203 isa tube. Preferably, the first elongate member 203 is flexible.Furthermore, the first elongate member 203 is preferably transparent or,at least, semi-transparent or semi-opaque. A degree of opticaltransparency allows a caregiver or user to inspect the lumen 207 forblockage or contaminants or to confirm the presence of moisture. Avariety of plastics, including medical grade plastics, are suitable forthe body of the first elongate member 203. Examples of suitablematerials include Polyolefin elastomers, Polyether block amides,Thermoplastic co-polyester elastomers, EPDM-Polypropylene mixtures, andThermoplastic polyurethanes.

In at least one embodiment, the extrudate used to form the firstelongate member 203 further comprises an antiblocking additive.Antiblocking additives can reduce the adhesion of two adjacent layers offilm. Antiblocking additives can include calcined kaolin (CaK), hydrouskaolin (HyK), calcium carbonate (CaC), talc (TaC), natural silica(NSi1), natural silica (NSi2), diatomaceous earth (DiE) and syntheticsilica (SSi). In some configurations, the antiblocking additive isfood-safe. In some embodiments, the antiblocking additive is talc. Theaddition of talc to the plastic extrudate advantageously reduces thestickiness of the resultant first elongate member 203. The addition oftalc to the extrudate also reduces the noise made when the firstelongate member 203 is dragged over an object, such as the edge of adesk or bedside table. In addition, the addition of talc reduces thenoise the tube makes when it is moved, flexed, and so forth by reducingthe extent to which adjacent bubbles stick (and unstick) to each otherwhen bunched (and unbunched) around the vicinity of a bend. In certainembodiments, the talc is in the range of 1.5 to 10 (or about 1.5 toabout 10) weight percent of the total extrudate. In certain embodiments,the talc is in the range of 1.5 to 5 (or about 1.5 to about 5) weightpercent of the total extrudate. In certain embodiments, the talc is inthe range of 10 (or about 10) weight percent or less of the totalextrudate. In certain embodiments, the talc is in the range of 5 (orabout 5) weight percent or less of the total extrudate. In certainembodiments, the talc is in the range of 1.5 (or about 1.5) weightpercent or more of the total extrudate. Desirably, the amount of talc islow enough that the tube will be reasonably clear to allow inspection ofthe inside of the tube.

The hollow body structure of the first elongate member 203 contributesto the insulating properties to the composite tube 201. An insulatingtube 201 is desirable because, as explained above, it prevents heatloss. This can allow the tube 201 to deliver gas from aheater-humidifier to a patient while maintaining the gas's conditionedstate with minimal energy consumption.

In at least one embodiment, the hollow portion of the first elongatemember 203 is filled with a gas. The gas can be air, which is desirablebecause of its low thermal conductivity (2.62×10⁻² W/m·K at 300K) andvery low cost. A gas that is more viscous than air may alsoadvantageously be used, as higher viscosity reduces convective heattransfer. Thus, gases such as argon (17.72×10⁻³ W/m·K at 300K), krypton(9.43×10⁻³ W/m·K at 300K), and xenon (5.65×10⁻³ W/m·K at 300K) canincrease insulating performance. Each of these gases is non-toxic,chemically inert, fire-inhibiting, and commercially available. Thehollow portion of the first elongated member 203 can be sealed at bothends of the tube, causing the gas within to be substantially stagnant.Alternatively, the hollow portion can be a secondary pneumaticconnection, such as a pressure sample line for conveying pressurefeedback from the patient-end of the tube to a controller. The firstelongate member 203 can be optionally perforated. For instance, thesurface of the first elongate member 203 can be perforated on anoutward-facing surface, opposite the lumen 207. In another embodiment,the hollow portion of the first elongate member 203 is filled with aliquid. Examples of liquids can include water or other biocompatibleliquids with a high thermal capacity. For instance, nanofluids can beused. An example nanofluid with suitable thermal capacity compriseswater and nanoparticles of substances such as aluminum.

The first elongate member 203 can contain a quantity of a fluid (such asair) and can be substantially sealed so as to prevent the quantity offluid escaping. In use, the fluid can be configured to be used tomeasure one or more properties of the tube 201, the first elongatemember 203, the second elongate member 205, and/or the gas travelingalong the tube 201. In at least one embodiment, the pressure of gaspassing along the tube can be measured. A reference measurement of thepressure of the fluid is made before gas begins to circulate. As gasbegins to pass through the tube 201, the pressure of the gas will tendto cause a proportional rise in the pressure of the fluid within thefirst elongate member 203. By comparing a measurement taken in use withthe reference measurement, the pressure of the gas within the tube 201can be determined. In another embodiment, a fluid is chosen that changesone or more properties based on the operational heat range of the gaswithin the tube 201. In this manner, by measuring the property of thefluid, the temperature of the gas can be determined. For example, afluid which expands with temperature can be used. In use, thetemperature of the fluid will tend towards the temperature of the gasflow. By then measuring the pressure of the fluid, the temperature ofthe fluid can be determined. This may have particular benefit when thetemperature of the gas flow is difficult or undesirable to measuredirectly.

In some embodiments, at least a portion of the first elongate member 203is formed of a material that allows vapor to pass through, for examplefor example, an activated perfluorinated polymer material with extremehydrophilic properties, such as NAFION, or a hydrophilic polyester blockcopolymer, such as SYMPATEX. Preferably, the portion of the firstelongate member 203 that forms the lumen of the tube 201 will be formedof the material. In use, a quantity of humidification fluid (such aswater) is passed through the space formed by the first elongate member.As the humidification fluid is heated (for example, by the heatingfilaments 215 disposed in the second elongate member 205), a portion ofthe humidification fluid will tend to evaporate. This can then passthrough the breathable portion into the gas flow, thereby humidifyingthe gas flow. In such an embodiment, the tube 201 may provide sufficienthumidification to the gas flow that a standalone humidifier can beomitted from the system.

In some embodiments, a gas flow can be passed along the space inside thefirst elongate member 203. For example, exhaled respiratory gases can becarried. In some embodiments, the first elongate member or at least aportion of the first elongate member (preferably the outer-facing side)can be made of a material that allows water vapor to pass therethrough,for example, an activated perfluorinated polymer material with extremehydrophilic properties, such as NAFION, or a hydrophilic polyester blockcopolymer, such as SYMPATEX. In this manner, as the exhaled gas travelsalong the length of the first elongate member, it will tend to dry fromabout 100% relative humidity at the patient-end to reduced humiditylevel at the opposite end.

The second elongate member 205 is also spirally wound and joined to thefirst elongate member 203 between adjacent turns of the first elongatemember 203. The second elongate member 205 forms at least a portion ofthe lumen 207 of the elongate tube. The second elongate member 205 actsas structural support for the first elongate member 203.

In at least one embodiment, the second elongate member 205 is wider atthe base (proximal the lumen 207) and narrower at the top. For example,the second elongate member can be generally triangular in shape,generally T-shaped, or generally Y-shaped. However, any shape that meetsthe contours of the corresponding first elongate member 203 is suitable.

Preferably, the second elongate member 205 is flexible, to facilitatebending of the tube. Desirably; the second elongate member 205 is lessflexible than the first elongate member 203. This improves the abilityof the second elongate member 205 to structurally support the firstelongate member 203. For example, the modulus of the second elongatemember 205 is preferably 30-50 MPa (or about 30-50 MPa). The modulus ofthe first elongate member 203 is less than the modulus of the secondelongate member 205. The second elongate member 205 can be solid ormostly solid. In addition, the second elongate member 205 canencapsulate or house conductive material, such as filaments, andspecifically heating filaments or sensors (not shown). Heating filamentscan minimize the cold surfaces onto which condensate from moisture-ladenair can form. Heating filaments can also be used to alter thetemperature profile of gases in the lumen 207 of composite tube 201. Avariety of polymers and plastics, including medical grade plastics, aresuitable for the body of the second elongate member 205. Examples ofsuitable materials include Polyolefin elastomers, Polyether blockamides, Thermoplastic co-polyester elastomers, EPDM-Polypropylenemixtures and Thermoplastic polyurethanes. In certain embodiments, thefirst elongate member 203 and the second elongate member 205 may be madefrom the same material. The second elongate member 205 may also be madeof a different color material from the first elongate member 203, andmay be transparent, translucent or opaque. For example, in oneembodiment the first elongate member 203 may be made from a clearplastic, and the second elongate member 205 may be made from an opaqueblue (or other color) plastic.

In some embodiments, the second elongate member 205 can be made of amaterial that wicks water. For example, an absorbent sponge-likematerial can be used. Preferably, the second elongate member 205 isconnected to a water source, such as a water bag. In use, water isconveyed along at least a portion of the length of the second elongatemember 205 (preferably, substantially the whole length). As gas passesalong the second elongate member 205, water vapor will tend to be pickedup by the gases, thereby humidifying the gas flow. In some embodiments,the one or more heater filaments embedded in the second elongate member205 can be controlled to alter the rate of evaporation and thereby alterthe level of humidification provided to the gas flow.

This spirally-wound structure comprising a flexible, hollow body and anintegral support can provide crush resistance, while leaving the tubewall flexible enough to permit short-radius bends without kinking,occluding or collapsing. Preferably, the tube can be bent around a 25 mmdiameter metal cylinder without kinking, occluding, or collapsing, asdefined in the test for increase in flow resistance with bendingaccording to ISO 5367:2000(E). This structure also can provide a smoothlumen 207 surface (tube bore), which helps keep the tube free fromdeposits and improves gas flow. The hollow body has been found toimprove the insulating properties of a tube, while allowing the tube toremain light weight.

As explained above, the composite tube 201 can be used as an expiratorytube and/or an inspiratory tube in a breathing circuit, or a portion ofa breathing circuit. Preferably, the composite tube 201 is used at leastas an inspiratory tube.

FIG. 37B shows a longitudinal cross-section of a top portion of theexample composite tube 201 of FIG. 37A. FIG. 37B has the sameorientation as FIG. 37A. This example further illustrates thehollow-body shape of the first elongate member 203. As seen in thisexample, the first elongate member 203 forms in longitudinalcross-section a plurality of hollow bubbles. Portions 209 of the firstelongate member 203 overlap adjacent wraps of the second elongate member205. A portion 211 of the first elongate member 203 forms the wall ofthe lumen (tube bore).

It was discovered that having a gap 213 between adjacent turns of thefirst elongate member 203, that is, between adjacent bubbles,unexpectedly improved the overall insulating properties of the compositetube 201. Thus, in certain embodiments, adjacent bubbles are separatedby a gap 213. Furthermore, certain embodiments include the realizationthat providing a gap 213 between adjacent bubbles increases the heattransfer resistivity (the R value) and, accordingly, decreases the heattransfer conductivity of the composite tube 201. This gap configurationwas also found to improve the flexibility of the composite tube 201 bypermitting shorter-radius bends. A T-shaped second elongate member 205,as shown in FIG. 37B, can help maintain a gap 213 between adjacentbubbles. Nevertheless, in certain embodiments, adjacent bubbles aretouching. For example, adjacent bubbles can be bonded together.

One or more conductive materials can be disposed in the second elongatemember 205 for heating or sensing the gas flow. In this example, twoheating filaments 215 are encapsulated in the second elongate member205, one on either side of the vertical portion of the “T.” The heatingfilaments 215 comprise conductive material, such as alloys of Aluminum(Al) and/or Copper (Cu), or conductive polymer. Preferably, the materialforming the second elongate member 205 is selected to be non-reactivewith the metal in the heating filaments 215 when the heating filaments215 reach their operating temperature. The filaments 215 may be spacedaway from lumen 207 so that the filaments are not exposed to the lumen207. At one end of the composite tube, pairs of filaments can be formedinto a connecting loop.

In at least one embodiment, a plurality of filaments are disposed in thesecond elongate member 205. The filaments can be electrically connectedtogether to share a common rail. For example, a first filament, such asa heating filament, can be disposed on a first side of the secondelongate member 205. A second filament, such as a sensing filament, canbe disposed on a second side of the second elongate member 205. A thirdfilament, such as a ground filament, can be disposed between the firstand second filaments. The first, second, and/or third filaments can beconnected together at one end of the second elongate member 205.

FIG. 37C shows a longitudinal cross-section of the bubbles in FIG. 37B.As shown, the portions 209 of the first elongate member 203 overlappingadjacent wraps of the second elongate member 205 are characterized by adegree of bond region 217. A larger bond region improves the tubesresistance to delamination at the interface of the first and secondelongate members. Additionally or alternatively, the shape of the beadand/or the bubble can be adapted to increase the bond region 217. Forexample, FIG. 37D shows a relatively small bonding area on the left-handside. FIG. 48B, discussed in greater detail herein, also demonstrates asmaller bonding region. In contrast, FIG. 37E has a much larger bondingregion than that shown in FIG. 37D, because of the size and shape of thebead. FIGS. 48A and 48C, discussed in greater detail herein, alsoillustrate a larger bonding region. It should be appreciated that,although the configurations in FIGS. 37E, 48A, and 48C may be preferredin certain embodiments, other configurations, including those of FIGS.37D, 48B, and other variations, may be utilized in other embodiments asmay be desired.

FIG. 37D shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 37D has the same orientation as FIG. 37B. Thisexample further illustrates the hollow-body shape of the first elongatemember 203 and demonstrates how the first elongate member 203 forms inlongitudinal cross-section a plurality of hollow bubbles. In thisexample, the bubbles are completely separated from each other by a gap213. A generally triangular second elongate member 205 supports thefirst elongate member 203.

FIG. 37E shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 37E has the same orientation as FIG. 37B. In theexample of FIG. 37E, the heating filaments 215 are spaced farther apartfrom each other than the filaments 215 in FIG. 37B. It was discoveredthat increasing the space between heating filaments can improve heatingefficiency, and certain embodiments include this realization. Heatingefficiency refers to the ratio of the amount of heat input to the tubeto the amount of energy output or recoverable from the tube. Generallyspeaking, the greater the energy (or heat) that is dissipated from thetube, the lower the heating efficiency. For improved heatingperformance, the heating filaments 215 can be equally (or about equally)spaced along the bore of the tube. Alternatively, the filaments 215 canbe positioned at extremities of the second elongate member 205, whichmay provide simpler manufacturing.

In FIG. 37F, the first elongate member 203 forms in longitudinalcross-section a plurality of hollow bubbles. In this example, there area plurality of bubbles, and more specifically, two adjacent wraps of thefirst elongate member 203, between wraps of the second elongate member205. This configuration is shown in greater detail in FIG. 37G. Asdescribed and shown elsewhere in this disclosure, certain configurationscan implement greater than two, for example, three, wraps of the firstelongate member 203 between wraps of the second elongate member 205.

Embodiments comprising a plurality of adjacent wraps of the firstelongate member 203 between wraps of the second elongate member 205 canbe advantageous because of improvements in overall tube flexibility. Thesubstantially solid second elongate member 205 is generally lessflexible than the hollow first elongate member 203. Accordingly, certainembodiments include the realization that overall tube flexibility can beimproved by increasing the number of bubbles of first elongate member203 between wraps of the second elongate member 205.

A first 300 mm-length sample of tube comprising two bubbles betweenwraps of the second elongate member 205 and a second 300 mm-lengthsample of tube comprising one bubble between wraps of the secondelongate member 205 were each tested on a flexibility jig. A front-plancross-sectional schematic of the flexibility jig is shown in FIG. 38A.The jig 1201 used a rod 1203 with a fixed mass of 120 g to apply a forceto each tube 201, which was positioned between two rollers 1205 and1207. The force exerted by the rod 1203 was about 1.2 N (0.12 kg*9.81m/s²). A detailed front-plan cross-sectional schematic of rollers 1205and 1207 is shown in FIG. 38B. Both rollers 1205 and 1207 had the samedimensions. The vertical deflection was measured using the position ofthe fixed weight with respect to a vertical support 1209 of theflexibility jig, shown in the photographs of FIGS. 38C through 38F.

FIG. 38C shows a front-perspective view of the second sample undertesting in the jig 1201. FIG. 38D shows a rear-perspective view of thesecond sample under testing in the jig 1201. FIG. 38E shows afront-perspective view of the first sample under testing in the jig1201. FIG. 38F shows a rear-perspective view of the first sample undertesting in the jig 1201. As shown in FIGS. 38C through 38F, the secondsample shown in FIGS. 38E and 38F had substantially greater verticaldeflection than the first sample shown in FIGS. 38C and 38D.Specifically, the second sample had a vertical deflection of 3 mm, whilethe first sample was much more flexible, having a vertical deflection of42 mm.

Another advantage of embodiments comprising a plurality of adjacentwraps of the first elongate member 203 between wraps of the secondelongate member 205 is improved recovery from crushing. It was observedthat, after crushing, samples having multiple bubbles between wraps ofthe first elongate member 203 recovered their shape more quickly thansamples having a single bubble between wraps of the first elongatemember 203.

Yet another advantage of embodiments comprising a plurality of adjacentwraps of the first elongate member 203 between wraps of the secondelongate member 205 is improved resistance to crushing. Crush resistanceis a mechanical property that plays an important role in the resilienceof the tube while in service. The hospital environment can be harsh, asthe tube can be subjected to crushing by a patient's arm or leg, bedframes, and other equipment.

Crush resistance testing was performed on four tube samples using anInstron machine set up as shown in the photograph in FIG. 39A. Thecylinder 1301 was plunged downwards 16 mm from the top of the tube at arate of 60 mm/min. The Instron machine has a load cell to accuratelymeasure force exerted on a component versus extension. The load vs.extension was plotted, as shown in FIG. 39B.

The crush stiffness for each sample was found by fitting a line of bestfit to the data of FIG. 39B and calculating its gradient. The calculatedcrush stiffness for each sample is shown in TABLE 1A. In TABLE 1A (andelsewhere in this disclosure), the designation “double bubble” refers toa sample of tube comprising two bubbles between wraps of the secondelongate member 205, when the sample is viewed in longitudinal crosssection. The designation “single bubble” refers to a sample of tubecomprising a single bubble between wraps of the second elongate member205, when the sample is viewed in longitudinal cross section. Theaverage crush stiffness (measured in N/mm) represents the averagemaximum force per unit width which produces no crush.

TABLE 1A Sample Crush Stiffness (N/mm) Average Double Bubble, Sample 13.26 3.21 Double Bubble, Sample 2 3.15 Single Bubble, Sample 1 3.98 3.86Single Bubble, Sample 2 3.74

As shown in the foregoing table, single bubble tubes had an averagecrush stiffness of 3.86 N/mm, while double bubble tubes had an averagecrush stiffness of 3.21 N/mm. In other words, the double bubble tubeshad an approximately 16.8% lower resistance to crush than the singlebubble tubes. Nevertheless, crush stiffness per unit thickness for thedouble bubble tubes was observed to be approximately 165% of the valuefor the single bubble tubes, as shown below in TABLE 1B.

TABLE 1B Bubble Thickness Crush Stiffness Stiffness/Bubble Thickness(mm) (N/mm) (N/mm²) Double 0.22 3.21 14.32 Bubble Single 0.43 3.86 8.70Bubble

Stated another way, when outer bubble thickness is taken into account,the double bubble tube is around 65% more resistant to crush than thesingle bubble tube variant. As shown in FIGS. 37F and 37G, the bubblesin the double bubble configuration are taller than they are wide, whichresults in more material in the vertical plane. Thus, it is believedthat the unexpected improvement in crush resistance per unit thicknessof the bubble may be attributed to the additional vertical web betweenbeads working in the direction of crush.

Tensile testing was also performed on the single and double bubble tubesamples. Both samples were 230 mm in length and were elongated by 15 mmat a rate of 10 mm/min. The force required to elongate the samples wasmeasured. The results are shown in TABLE 1C.

TABLE 1C Sample Peak Force at 15 mm extension (N) Double Bubble 17.60Single Bubble 54.65

As shown in TABLE 1C, the double bubble tube was significantlystretchier in the axial (longitudinal) plane. This increase inlongitudinal stretchiness is believed to be due to the single bubbletube having more material in between the beads that are working in theaxial plane.

Yet another advantage to the multiple-bubble configuration describedabove is that the configuration imparts the ability to hold or transportadditional fluids. As explained above, the hollow portion of the firstelongate member 203 can be filled with a gas. The multiple discretebubbles or hollow portions can be filled with multiple discrete gases.For example, one hollow portion can hold or transport a first gas and asecond hollow portion can be used as a secondary pneumatic connection,such as a pressure sample line for conveying pressure feedback from thepatient-end of the tube to a controller. As another example, multiplediscrete bubbles or hollow portions can be filled with a combination ofliquids, or a combination of liquids and gases. A first bubble can holdor transport a gas, and a second bubble can hold or transport a liquid,for instance. Suitable liquids and gases are described above.

It should be appreciated that, although the configurations in FIGS. 37Fand 37G may be preferred in certain embodiments, other configurations,may be utilized in other embodiments as may be desired.

Referring now to FIGS. 37H-37L and 37V-37Z, some variations of the tube201 are shown which are adapted to provide increased lateral stretch inthe tube. FIGS. 37V-37Z show a stretched state of the tubes shown inFIGS. 37H-37L, respectively.

Certain embodiments include the realization that the tubes shown inFIGS. 37H, 37I, and 37L comprise a second elongate member 205 having ashape that increases stretch capability. For example, in FIG. 37H, thesecond elongate member 205 is substantially oblate having a profilesubstantially the same height as the first elongate member 203. As shownin FIG. 37V, this allows the second elongate member 205 to deformoutwards to at least twice the width compared to the second elongatemember 205 at rest.

In FIGS. 37I and 37L, the second elongate member 205 is shaped so as tohave an accordion-like shape. On stretching, the second elongate member205 can therefore accommodate an increase amount of stretching byflattening (as shown in FIGS. 37W and 37Z, respectively).

In FIGS. 37J and 37K, the first elongate member 203 is given a shapethat allows it to deform outward, thereby allowing an increased lateralstretch (as shown in FIGS. 37X and 37Y, respectively).

Reference is next made to FIGS. 40A through 40H which demonstrateexample configurations for the second elongate member 205. FIG. 40Ashows a cross-section of a second elongate member 205 having a shapesimilar to the T-shape shown in FIG. 37B. In this example embodiment,the second elongate member 205 does not have heating filaments. Othershapes for the second elongate member 205 may also be utilized,including variations of the T-shape as described below and triangularshapes.

FIG. 40B shows another example second elongate member 205 having aT-shape cross-section. In this example, heating filaments 215 areembedded in cuts 301 in the second elongate member 205 on either side ofthe vertical portion of the “T.” In some embodiments, the cuts 301 canbe formed in the second elongate member 205 during extrusion. The cuts301 can alternatively be formed in the second elongate member 205 afterextrusion. For example, a cutting tool can form the cuts in the secondelongate member 205. Preferably, the cuts are formed by the heatingfilaments 215 as they are pressed or pulled (mechanically fixed) intothe second elongate member 205 shortly after extrusion, while the secondelongate member 205 is relatively soft. Alternatively, one or moreheating filaments can be mounted (e.g., adhered, bonded, or partiallyembedded) on the base of the elongate member, such that the filament(s)are exposed to the tube lumen. In such embodiments, it can be desirableto contain the filament(s) in insulation to reduce the risk of fire whena flammable gas such as oxygen is passed through the tube lumen.

FIG. 40C shows yet another example second elongate member 205 incross-section. The second elongate member 205 has a generally triangularshape. In this example, heating filaments 215 are embedded on oppositesides of the triangle.

FIG. 40D shows yet another example second elongate member 205 incross-section. The second elongate member 205 comprises four grooves303. The grooves 303 are indentations or furrows in the cross-sectionalprofile. In some embodiments, the grooves 303 can facilitate theformation of cuts (not shown) for embedding filaments (not shown). Insome embodiments, the grooves 303 facilitate the positioning offilaments (not shown), which are pressed or pulled into, and therebyembedded in, the second elongate member 205. In this example, the fourinitiation grooves 303 facilitate placement of up to four filaments,e.g., four heating filaments, four sensing filaments, two heatingfilaments and two sensing filaments, three heating filaments and onesensing filament, or one heating filament and three sensing filaments.In some embodiments, heating filaments can be located on the outside ofthe second elongate member 205. Sensing filaments can be located on theinside.

FIG. 40E shows still another example second elongate member 205 incross-section. The second elongate member 205 has a T-shape profile anda plurality of grooves 303 for placing heating filaments.

FIG. 40F shows yet another example second elongate member 205 incross-section. Four filaments 215 are encapsulated in the secondelongate member 205, two on either side of the vertical portion of the“T.” As explained in more detail below, the filaments are encapsulatedin the second elongate member 205 because the second elongate member 205was extruded around the filaments. No cuts were formed to embed theheating filaments 215. In this example, the second elongate member 205also comprises a plurality of grooves 303. Because the heating filaments215 are encapsulated in the second elongate member 205, the grooves 303are not used to facilitate formation of cuts for embedding heatingfilaments. In this example, the grooves 303 can facilitate separation ofthe embedded heating filaments, which makes stripping of individualcores easier when, for example, terminating the heating filaments.

FIG. 40G shows yet another example second elongate member 205 incross-section. The second elongate member 205 has a generally triangularshape. In this example, the shape of the second elongate member 205 issimilar to that of FIG. 40C, but four filaments 215 are encapsulated inthe second elongate member 205, all of which are central in the bottomthird of the second elongate member 205 and disposed along a generallyhorizontal axis.

As explained above, it can be desirable to increase the distance betweenfilaments to improve heating efficiency. In some embodiments, however,when heating filaments 215 are incorporated into the composite tube 201,the filaments 215 can be positioned relatively central in the secondelongate member 205. A centralized position promotes robustness of thecomposite tubing for reuse, due in part to the position reducing thelikelihood of the filament breaking upon repeating flexing of thecomposite tube 201. Centralizing the filaments 215 can also reduce therisk of an ignition hazard because the filaments 215 are coated inlayers of insulation and removed from the gas path.

As explained above, some of the examples illustrate suitable placementsof filaments 215 in the second elongate member 205. In the foregoingexamples comprising more than one filament 215, the filaments 215 aregenerally aligned along a horizontal axis. Alternative configurationsare also suitable. For example, two filaments can be aligned along avertical axis or along a diagonal axis. Four filaments can be alignedalong a vertical axis or a diagonal axis. Four filaments can be alignedin a cross-shaped configuration, with one filament disposed at the topof the second elongate member, one filament disposed at the bottom ofthe second elongate member (near the tube lumen), and two filamentsdisposed on opposite arms of a “T,” “Y,” or triangle base.

Referring now to FIG. 40H, an alternative embodiment of the secondelongate member 205 is shown. The second elongate member 205 comprisesone or more coaxial cables 1901 having a conductor 1902 surrounded by aninsulation layer 1903, a shield layer 1904, and a sheath layer 1905. Incertain embodiments, one or more of cables 1901 can be a multi-axialcable, that is, have multiple conductors 1902 arranged within theinsulation layer 1903. In this manner, a single assembly containingmultiple wires (including heater wires and/or sensor wires) can be usedin the second elongate member 205, thereby simplifying assembly andproviding some shielding (via the shield layer 1904) from RFinterference and the like.

In some embodiments, one or more data transmission cables can beincluded in the second elongate member 205. The data transmission cablescan comprise fiber optic cables. In at least one embodiment, a singlefiber optic cable is included in the second elongate member 205 and usedin a passive mode. In a passive mode, at a first end of the cable, alight source and a light sensor are provided. At a second end, areflector is provided. In use, the light source provides a quantity oflight having certain properties towards the reflector. The reflectorthen reflects the light towards the light sensor, which can analyze thereflected light to determine the properties of the light. The reflectorcan be adapted to change the property of the reflected light dependingon a property of the system. For example, the reflector can be used tomonitor condensation within the interface. The reflector can comprise amaterial which, for example, changes color depending on the presence ofcondensation at the second end. The reflector can alternatively oradditionally include a material which changes color or the likedepending on the level of humidity (either relative humidity or absolutehumidity) and/or the temperature of gas at the second end.

TABLES 2A and 2B show some example dimensions of medical tubes describedherein, as well as some ranges for these dimensions. The dimensionsrefer to a transverse cross-section of a tube. In these tables, lumendiameter represents the inner diameter of a tube. Pitch represents thedistance between two repeating points measured axially along the tube,namely, the distance between the tip of the vertical portions ofadjacent “T”s of the second elongate member. Bubble width represents thewidth (maximum outer diameter) of a bubble. Bubble height represents theheight of a bubble from the tube lumen. Bead height represents themaximum height of the second elongate member from the tube lumen (e.g.,the height of the vertical portion of the “T”). Bead width representsthe maximum width of the second elongate member (e.g., the width of thehorizontal portion of the “T”). Bubble thickness represents thethickness of the bubble wall.

TABLE 2A Infant Adult Dimension Range Dimension Range Feature (mm) (±)(mm) (±) Lumen diameter 11 1 18 5 Pitch 4.8 1 7.5 2 Bubble width 4.2 1 71 Bead width 2.15 1 2.4 1 Bubble height 2.8 1 3.5 0.5 Bead height 0.90.5 1.5 0.5 Bubble thickness 0.4 0.35 0.2 0.15

TABLE 2B Infant Adult Dimension Range Dimension Range Feature (mm) (±)(mm) (±) Lumen diameter 11 1 18 5 Pitch 4.8 1 7.5 2 Bubble width 4.2 1 71 Bead width 2.15 1 3.4 1 Bubble height 2.8 1 4.0 0.5 Bead height 0.90.5 1.7 0.5 Bubble thickness 0.4 0.35 0.2 0.15

In another example embodiment, a medical tube has the approximatedimensions shown in TABLE 2C.

TABLE 2C Dimension Range Feature (mm) (+/−) Pitch 5.1 3.0 Bubble width5.5 2.0 Bubble height 3.2 2.0 Bubble thickness on top, farthest fromlumen 0.24 +0.20/−0.10 (outer wall thickness) Bubble thickness adjacentlumen (inner wall 0.10 +0.20/−0.05 thickness) Outer diameter of tube22.5 3.0 Inner diameter of tube 17.2 4.0

The dimensions shown in TABLE 2C can be particularly advantageous forobstructive sleep apnea (OSA) applications. Compared to conduits used inrespiratory care, conduits used in OSA applications desirably are moreflexible, have a smaller outer diameter, have less weight, and arequieter and less tacky to the touch.

In order to improve flexibility, the conduit can be formed to have areduced pitch. In some configurations, the first elongate member can beformed into a conduit having a pitch of between about 2 mm and about 8mm. In some configurations, the conduit can have a pitch of betweenabout 4.5 mm to about 5.6 mm. In some configurations, the conduit canhave a pitch of about 5.1 mm. In some configurations, the conduit canincorporate a heater, have an internal diameter of about 17 mm and havea length of about 72 inches (183 cm) while including a pitch of betweenabout 5 and 5.1 mm. In such configurations, the resistance of theheater, which is a function of the length of the first elongate member(and the second elongate member that contains the heater and that ispositioned alongside the first elongate member), can have an acceptablelevel of resistance for use with a CPAP or otherwise within the OSAfield. In some configurations, the first elongate member can be formedinto a conduit and, as such, the first elongate member has a portionhaving a first thickness that defines a lumen within the conduit and asecond portion having a second thickness that defines at least a portionof the outer surface of the conduit. In some such configurations, thefirst thickness is less than the second thickness. Surprisingly, whenthe first thickness is less than the second thickness, the conduitexhibits more flexibility as compared to simply reducing the thicknessthroughout the first elongate member. In some such configurations, thefirst thickness is about 0.16 mm and the second thickness is about 0.22mm. In some configurations, the conduit can incorporate a heater, havean internal diameter of about 17 mm and have a length of about 72 inches(183 cm) while having a weight of between about 85 grams and about 90grams.

In order to make the conduit quieter as it is moved or dragged along asurface, the first elongate member can be formed to have a reduced wallthickness and the wall can be soft and deformable. In someconfigurations, the first elongate member can be formed to have a wallthickness of between about 0.05 mm and about 44 mm. In someconfigurations, the first elongate member can be formed to have a wallthickness of between about 0.13 mm and about 0.44 mm. In someconfigurations, the first elongate member can be formed to have a wallthickness of between about 0.13 mm and about 0.26 mm. In someconfigurations, the first elongate member can be formed to have a wallthickness of between about 0.16 mm and about 0.24 mm. In someconfigurations, the first elongate member can be formed to have a wallthickness of between about 0.17 mm and about 0.225 mm. Forming theelongate member with a reduced thickness also has the effect of reducingthe overall weight of the conduit.

In order to reduce the size of the conduit, the diameter can be reducedwhile maintaining a sufficient diameter to reduce the likelihood of anunacceptable pressure drop. In some configurations, the internaldiameter can be between about 13 mm and about 22 mm. In someconfigurations, the internal diameter can be between about 16 mm andabout 19 mm. In some configurations, the conduit can have an outerdiameter of about 22.5 mm. In some configurations, the conduit can havean outer diameter of about 22.5 mm, an internal diameter of about 17.2mm and a length of about 72 inches (183 cm). Such a configurationresults in a suitable pressure drop of the length of the conduit whileproviding a desired reduction in size to the conduit while having aconduit with a bubble extending around an outer periphery of theconduit, which otherwise would result in an undesired increase in sizewhen compared to standard corrugated tubing.

In order to provide a desired tactile experience, the conduit desirablyhas an improved surface texture. Surprisingly, the improvement to thesurface texture also has resulted in a quieter conduit in use. In someconfigurations, the first elongate member can be formed from anextrudate that includes an antiblocking additive. The antiblockingadditive, as discussed above, can reduce sticking between layers of theconduit, which has been discovered to help in reducing noise levelsassociated with the conduit (e.g., when dragging the conduit over acorner of furniture or the like). In some configurations, the firstelongate member can be formed from an extrudate that includes talc. Insome configurations, the first elongate member can be formed from anextrudate that includes between about 1.5 weight percent and about 10weight percent talc. In some configurations, the first elongate membercan be formed from an extrudate that includes between about 1.5 weightpercent and about 3 weight percent talc. In some configurations, thefirst elongate member can be formed from an extrude that includes about1.5 weight percent talc.

TABLES 3A and 3B provide example ratios between the dimensions of tubefeatures for the tubes described in TABLES 2A and 2B respectively.

TABLE 3A Ratios Infant Adult Lumen diameter:Pitch 2.3:1 2.4:1Pitch:Bubble width 1.1:1 1.1:1 Pitch:Bead width 2.2:1 3.1:1 Bubblewidth:Bead width 2.0:1 2.9:1 Lumen diameter:Bubble height 3.9:1 5.1:1Lumen diameter:Bead height 12.2:1  12.0:1  Bubble height:Bead height3.1:1 2.3:1 Lumen diameter:Bubble thickness 27.5:1  90.0:1 

TABLE 3B Ratios Infant Adult Lumen diameter:Pitch 2.3:1 2.4:1Pitch:Bubble width 1.1:1 1.1:1 Pitch:Bead width 2.2:1 2.2:1 Bubblewidth:Bead width 2.0:1 2.1:1 Lumen diameter:Bubble height 3.9:1 4.5:1Lumen diameter:Bead height 12.2:1  10.6:1  Bubble height:Bead height3.1:1 2.4:1 Lumen diameter:Bubble thickness 27.5:1  90.0:1 

The following tables show some example properties of a composite tube(labeled “A”), described herein, having a heating filament integratedinside the second elongate member. For comparison, properties of aFisher & Paykel model RT100 disposable corrugated tube (labeled “B”)having a heating filament helically wound inside the bore of the tubeare also presented.

Measurement of resistance to flow (RTF) was carried out according toAnnex A of ISO 5367:2000(E). The results are summarized in TABLE 4. Asseen below, the RTF for the composite tube is lower than the RTF for themodel RT100 tube.

TABLE 4 RTF (cm H₂O) Flow rate (L/min) 3 20 40 60 A 0 0.05 0.18 0.38 B 00.28 0.93 1.99

Condensate or “rainout” within the tube refers to the weight ofcondensate collected per day at 20 L/min gas flow rate and roomtemperature of 18° C. Humidified air is flowed through the tubecontinuously from a chamber. The tube weights are recorded before andafter each day of testing. Three consecutive tests are carried out withthe tube being dried in between each test. The results are shown belowin TABLE 5. The results showed that rainout is significantly lower inthe composite tube than in the model RT100 tube.

TABLE 5 Tube A A A B B B (Day 1) (Day 2) (Day 3) (Day 1) (Day 2) (day 3)Weight 136.20 136.70 136.70 111.00 111.10 111.10 before (g) Weight139.90 140.00 139.20 190.20 178.80 167.10 after (g) Condensate 3.7 3.32.5 79.20 67.70 56.00 weight (g)

The power requirement refers to the power consumed during the condensatetest. In this test, the ambient air was held at 18° C. Humidificationchambers, such as humidification chamber 46 in FIG. 1, were powered byMR850 heater bases. The heating filaments in the tubes were poweredindependently from a DC power supply. Different flow rates were set andthe chamber was left to settle to 37° C. at the chamber output. Then,the DC voltage to the circuits was altered to produce a temperature of40° C. at the circuit output. The voltage required to maintain theoutput temperature was recorded and the resulting power calculated. Theresults are shown in TABLE 6. The results show that composite Tube Auses significantly more power than Tube B. This is because Tube B uses ahelical heating filament in the tube bore to heat the gas from 37° C. to40° C. The composite tube does not tend to heat gas quickly because theheating filament is in the wall of the tube (embedded in the secondelongate member). Instead, the composite tube is designed to maintainthe gas temperature and prevent rainout by maintaining the tube bore ata temperature above the dew point of the humidified gas.

TABLE 6 Flow rate (L/min) 40 30 20 Tube A, power required (W) 46.8 38.537.8 Tube B, power required (W) 28.0 27.5 26.8

Tube flexibility was tested by using a three-point bend test. Tubes wereplaced in a three point bend test jig and used along with an Instron5560 Test System instrument, to measure load and extension. Each tubesample was tested three times; measuring the extension of the tubeagainst the applied load, to obtain average respective stiffnessconstants. The average stiffness constants for Tube A and Tube B arereproduced in TABLE 7.

TABLE 7 Tube Stiffness (N/mm) A 0.028 B 0.088

Methods Of Manufacture

Reference is next made to FIGS. 41A through 41F which demonstrateexample methods for manufacturing composite tubes.

Turning first to FIG. 41A, in at least one embodiment, a method ofmanufacturing a composite tube comprises providing the second elongatemember 205 and spirally wrapping the second elongate member 205 around amandrel 401 with opposite side edge portions 403 of the second elongatemember 205 being spaced apart on adjacent wraps, thereby forming asecond-elongate-member spiral 405. The second elongate member 205 may bedirectly wrapped around the mandrel in certain embodiments. In otherembodiments, a sacrificial layer may be provided over the mandrel.

In at least one embodiment, the method further comprises forming thesecond elongate member 205. Extrusion is a suitable method for formingthe second elongate member 205. The second extruder can be configured toextrude the second elongate member 205 with a specified bead height.Thus, in at least one embodiment, the method comprises extruding thesecond elongate member 205.

As shown in FIG. 41B, extrusion can be advantageous because it can allowheating filaments 215 to be encapsulated in the second elongate member205 as the second elongate member is formed 205, for example, using anextruder having a cross-head extrusion die. Thus, in certainembodiments, the method comprises providing one or more heatingfilaments 215 and encapsulated the heating filaments 215 to form thesecond elongate member 205. The method can also comprise providing asecond elongate member 205 having one or more heating filaments 215embedded or encapsulated in the second elongate member 205.

In at least one embodiment, the method comprises embedding one or morefilaments 215 in the second elongate member 205. For example, as shownin FIG. 41C, filaments 215 can be pressed (pulled or mechanicallypositioned) into the second elongate member 205 to a specified depth.Alternatively, cuts can be made in the second elongate member 205 to aspecified depth, and the filaments 215 can be placed into the cuts.Preferably, pressing or cutting is done shortly after the secondelongate member 205 is extruded and the second elongate member 205 issoft.

As shown in FIGS. 41D and 41E, in at least one embodiment, the methodcomprises providing the first elongate member 203 and spirally wrappingthe first elongate member 203 around the second-elongate-member spiral405, such that portions of the first elongate member 203 overlapadjacent wraps of the second-elongate-member spiral 405 and a portion ofthe first elongate member 203 is disposed adjacent the mandrel 401 inthe space between the wraps of the second-elongate-member spiral 405,thereby forming a first-elongate-member spiral 407. FIG. 41D shows suchan example method, in which heating filaments 215 are encapsulated inthe second elongate member 205, prior to forming thesecond-elongate-member spiral. FIG. 41E shows such an example method, inwhich heating filaments 215 are embedded in the second elongate member205, as the second-elongate-member spiral is formed. An alternativemethod of incorporating filaments 215 into the composite tube comprisesencapsulating one or more filaments 215 between the first elongatemember 203 and the second elongate member 205 at a region where thefirst elongate member 203 overlaps the second elongate member 205.

As discussed above, at least one embodiment comprises a tube havingmultiple wraps of the first elongate member 203 between wraps of thesecond elongate member 205. Accordingly, in certain embodiments, themethod comprises providing the first elongate member 203 and spirallywrapping the first elongate member 203 around the second-elongate-memberspiral 405, such that a first side portion of the first elongate member203 overlaps a wrap of the second-elongate-member spiral 405 and asecond side portion of the first elongate member 203 contacts anadjacent side portion of the first elongate member 203. A portion of thefirst elongate member 203 is disposed adjacent the mandrel 401 in thespace between the wraps of the second-elongate-member spiral 405,thereby forming a first-elongate-member spiral 407 comprising multiplewraps of the first elongate member 203 between wraps of the secondelongate member 205.

In at least one embodiment, the first elongate member 203 is wrappedmultiple times between winds of the second elongate member 205. Anexample schematic of the resulting longitudinal cross-section is shownin FIG. 41G. Adjacent wraps of the first elongate member 203 can befused using any suitable technique, such as heat fusing, adhesive, orother attachment mechanism. In at least one embodiment, adjacent moltenor softened bubbles can be touched together and thereby bonded while hotand subsequently cooled with an air jet. Adjacent wraps of the firstelongate member 203 can also be joined by winding them on the mandrel ina softened state and allowing them to cool.

In at least one embodiment, the first elongate member 203 is wrapped asingle time or multiple times between winds of the second elongatemember 205, and the bubble or bubbles between winds of the secondelongate member 205 are further collapsed into additional discretebubbles using an appropriate technique such as a heat treatment. Anexample schematic of the resulting longitudinal cross-section is shownin FIG. 41H. As shown in FIG. 41H, one bubble of the first elongatemember 203 can be collapsed into two or three or more discrete bubblesusing any suitable technique, such as application of a mechanical forcewith an object or application of a force with a directed air jet.Another example schematic of a resulting longitudinal cross-section isshown in FIG. 41I. In this example, a center portion of a bubble iscollapsed such that the top of the bubble is bonded to the bottom of thebubble to form two discrete bubbles separated by a flat bottom portion.Then, adjacent side portions of the two discrete bubbles are bonded toform a structure comprising three discrete bubbles.

The above-described alternatives for incorporating one or more heatingfilaments 215 into a composite tube have advantages over the alternativeof having heating filaments in the gas path. Having the heatingfilament(s) 215 out of the gas path improves performance because thefilaments heat the tube wall where the condensation is most likely toform. This configuration reduces fire risk in high oxygen environmentsby moving the heating filament out of the gas path. This feature alsoreduces performance as it reduces the heating wires effectiveness atheating the gases that are passing through the tube. Nevertheless, incertain embodiments, a composite tube 201 comprises one or more heatingfilaments 215 placed within the gas path. For example, heating filamentscan be emplaced on the lumen wall (tube bore), for example, in a spiralconfiguration. An example method for disposing one or more heatingfilaments 215 on the lumen wall comprises bonding, embedding, orotherwise forming a heating filament on a surface of the second elongatemember 205 that, when assembled, forms the lumen wall. Thus, in certainembodiments, the method comprises disposing one or more heatingfilaments 215 on the lumen wall.

Regardless of whether the heating filaments 215 are embedded orencapsulated on the second elongate member 205 or disposed on the secondelongate member 205, or otherwise placed in or on the tube, in at leastone embodiment, pairs of filaments can be formed into a connecting loopat one end of the composite tube to form a circuit.

FIG. 41F shows a longitudinal cross-section of the assembly shown inFIG. 41E, focusing on a top portion of the mandrel 401 and a top portionof the first-elongate-member spiral 407 and second-elongate-memberspiral 405. This example shows the second-elongate-member spiral 405having a T-shaped second elongate member 205. As the second-elongatemember is formed, heating filaments 215 are embedded in the secondelongate member 205. The right side of FIG. 41F shows the bubble-shapedprofile of the first-elongate-member spiral, as described above.

The method can also comprise forming the first elongate member 203.Extrusion is a suitable method for forming the first elongate member203. Thus, in at least one embodiment, the method comprises extrudingthe first elongate member 203. The first elongate member 203 can also bemanufactured by extruding two or more portions and joining them to forma single piece. As another alternative, the first elongate member 203can also be manufactured by extruding sections that produce a hollowshape when formed or bonded adjacently on a spiral-tube forming process.

The method can also comprise supplying a gas at a pressure greater thanatmospheric pressure to an end of the first elongate member 203. The gascan be air, for example. Other gases can also be used, as explainedabove. Supplying a gas to an end of the first elongate member 203 canhelp maintain an open, hollow body shape as the first elongate member203 is wrapped around the mandrel 401. The gas can be supplied beforethe first elongate member 203 is wrapped around the mandrel 401, whilethe first elongate member 203 is wrapped around the mandrel 401, orafter the first elongate member 203 is wrapped around the mandrel 401.For instance, an extruder with an extrusion die head/tip combination cansupply or feed air into the hollow cavity of the first elongate member203 as the first elongate member 203 is extruded. Thus, in at least oneembodiment, the method comprises extruding the first elongate member 203and supplying a gas at a pressure greater than atmospheric pressure toan end of the first elongate member 203 after extrusion. A pressure of15 to 30 cm H₂O-(or about 15 to 30 cm H₂O) has been found to besuitable.

In at least one embodiment, the first elongate member 203 and the secondelongate member 205 are spirally wound about the mandrel 401. Forexample, the first elongate member 203 and second elongate member 205may come out of an extrusion die at an elevated temperature of 200° C.(or about 200° C.) or more and then be applied to the mandrel after ashort distance. Preferably, the mandrel is cooled using a water jacket,chiller, and/or other suitable cooling method to a temperature of 20° C.(or about 20° C.) or less, e.g., approaching 0° C. (or about 0° C.).After 5 (or about 5) spiral wraps, the first elongate member 203 andsecond elongate member 205 are further cooled by a cooling fluid (liquidor gas). In one embodiment, the cooling fluid is air emitted from a ringwith jets encircling the mandrel. After cooling and removing thecomponents from the mandrel, a composite tube is formed having a lumenextending along a longitudinal axis and a hollow space surrounding thelumen. In such an embodiment, no adhesive or other attachment mechanismis needed to connect the first and second elongate members. Otherembodiments may utilize an adhesive or other attachment mechanism tobond or otherwise connect the two members. In another embodiment, thesecond elongate member 205 after extrusion and placement of the heatingfilaments may be cooled to freeze the location of the heating filaments.The second elongate member 205 may then be re-heated when applied to themandrel to improve bonding. Example methods for re-heating include usingspot-heating devices, heated rollers, etc.

The method can also comprise formed pairs of heating or sensingfilaments into a connecting loop at one end of the composite tube. Forexample, end sections of two heating or sensing filaments can beextricated from the second elongate member 205 and then formed into aconnecting loop e.g., by tying, bonding, adhering, fusing, etc the twofilaments together. As another example, end sections of the heatingfilaments can be left free from the second elongate member 205 duringthe manufacturing process and then formed into a connecting loop whenthe composite tube is assembled.

With reference now to FIGS. 41J-41Q, an alternative method of forming atube 201 involves an extrusion tool 2001 having a series of flow pathsrunning therealong. The extrusion tool 2001 can be used to form tubessuch as the example tubes shown in FIGS. 41P and 41Q. As shown, tubesproduced using the extrusion tool 2001 can include a plurality of firstelongate members 203 extending generally along the longitudinal axis ofthe tube. In some embodiments, the extrusion tool 2001 includes a body2010 and a central extension 2020. In some embodiments, the body 2010and extension 2020 are generally cylindrical. The body 2010 can includeone or more flow paths 2012 that allow for the passage of a moltenplastic or another material through the body 2010 from an input end 2014to an output or extrusion end 2016. In some embodiments, the flow pathshave a substantially conical longitudinal cross-section (that is, arewider where the molten plastic first enters at the input 2014 andnarrower near the extrusion end 2016). The flow paths can have variousconfigurations to produce tubes 201 having various profiles. Forexample, the flow path configuration shown at the output or extrusionend 2016 in FIGS. 41L and 41M can produce a tube 201 having an end viewprofile as shown in FIG. 41J. FIG. 41K shows an end view of the tube ofFIG. 41J including second elongate members 205, which may includeheating filaments 215, disposed between adjacent bubbles or firstelongate members 203. In use, the tool 2001 is adapted to rotate so asto induce the tube 201 to be helically formed. As shown in FIG. 410, thecentral extension 2020 can couple the extrusion tool 2001 to an extruder2030. Bearings 2022 disposed between the central extension 2020 and theextruder 2030 can allow the central extension 2020 and body 2010 torotate relative to the extruder 2030. The rate of rotation of the tool2001 can be adjusted to change the pitch or helix angle of the firstelongate members 203. For example, a faster rate of rotation can producea smaller helix angle, as shown in FIG. 41P. A slower rate of rotationcan produce a larger helix angle, as shown in FIG. 41Q.

Medical Tubes Having A Single Spirally Wound Tube

FIGS. 42A-42F show transverse cross-sections of example embodiments oftubes comprising a single tube-shaped element having a first elongatemember or portion 203 and a second elongate member or portion 205. Asillustrated, the second elongate portions 205 are integral with thefirst elongate portions 203, and extend along the entire length of thesingle tube-shaped element. In the embodiments illustrated, the singletube-shaped element is an elongate hollow body having in transversecross-section a relatively thin wall defining in part the hollow portion501, with two reinforcement portions 205 with a relatively greaterthickness or relatively greater rigidity on opposite sides of theelongate hollow body adjacent the relatively thin wall. Thesereinforcement portions form a portion of the inner wall of the lumen 207after the elongate hollow body is spirally wound, such that thesereinforcement portions are also spirally positioned between adjacentturns of the elongate hollow body.

In at least one embodiment, the method comprises forming an elongatehollow body comprising the first elongate portion 203 and thereinforcement portion 205. Extrusion is a suitable method for formingthe elongate hollow body. Suitable cross-sectional shapes for thetube-shaped element are shown in FIGS. 42A-42F.

The elongate hollow body can be formed into a medical tube, as explainedabove, and the foregoing discussion is incorporated by this reference.For example, in at least one embodiment, a method of manufacturing amedical tube comprises spirally wrapping or winding the elongate hollowbody around a mandrel. This may be done at an elevated temperature, suchthat the elongate hollow body is cooled after being spirally wound tojoin adjacent turns together As shown in FIG. 42B, opposite side edgeportions of the reinforcement portions 205 can touch on adjacent turns.In other embodiments, opposite side edge portions of the second elongatemember 205 can overlap on adjacent turns, as shown in FIGS. 42D and 42E.Heating filaments 215 can be incorporated into the second elongatemember as explained above and as shown in FIGS. 42A through 42F. Forexample, heating filaments may be provided on opposite sides of theelongate hollow body such as shown in FIGS. 42A-42D. Alternatively,heating filaments may be provided on only one side of the elongatehollow body, such as shown in FIGS. 42E-42F. Any of these embodimentscould also incorporate the presence of sensing filaments.

Placement of Chamber-End Connector with Electrical Connectivity

Reference is next made to FIG. 43A, which shows an example flow chartfor attaching a connector to the end of the tube that is configured inuse to connect to a humidifier. For example, as described above withreference to FIG. 1, the inspiratory conduit 70 connects to thehumidification unit 40 via inlet 42. The example flow chart of FIG. 43Acan make the inspiratory conduit 70 capable of physically andelectrically connecting to the humidification unit 40.

In the example of FIG. 43A, a seal 1503 is inserted into a seal housing1501. The act of seal insertion is also shown in greater detail in FIG.43B. The seal housing 1501 is made of a molded plastic. One open end issized and configured for connecting to a humidifier. The seal 1503 canbe an o-ring, as shown in FIG. 43B. A suitable configuration for theo-ring can be a double-toric configuration comprising thicker concentrictoruses connected by a thinner web. In this example, the o-ring ismolded from a single elastomeric material, such as rubber. The seal 1503is seated in a compliant ridge in the seal housing 1501. The seal 1503is designed to seal against an outer surface of the port of thehumidifier chamber. The seal 1503 can deflect to extend along the outersurface of the port. In other words, the double o-ring configurationincludes an inner O-ring and an outer O-ring connected by a flange. Theouter O-ring will be sealed within the connector while the inner O-ringcan deflect along the flange portion and squeeze against the outersurface of the port. In such a position, a horizontal plane extendingthrough a center axis of the inner O-ring may be in a different planethan a horizontal plane extending through a center axis of the outerO-ring.

Turning again to the example of FIG. 43A, a printed circuit board (PCB)is inserted into a compliant dock on the seal housing 1501. The act ofPCB insertion is shown in greater detail in FIG. 43C. In FIG. 43C, anassembly 1505 comprising a PCB and a PCB connector is inserted into acompliant dock on the seal housing 1501. In this example, the PCBconnector is an off-the-shelf connector sold by Tyco Electronics Corp.(Berwyn, Pa.). The PCB comprises four terminals suitable for receivingfour conductive filaments encased in the second elongate member of thetube. However, the PCB can be configured to receive a suitable number ofconductive filaments, if the second elongate member contains more orfewer than four conductive filaments.

Turning again to the example of FIG. 43A, a seal retainer 1507 isclipped onto one open end of the seal housing 1501 with the seal 1503seated on the compliant ridge. Clipping the seal retainer 1507 in placecompresses the seal 1503 and thereby forms a liquid- and gas-resistantconnection between the seal housing 1501 and the seal retainer 1507. Inthis example, the seal retainer is made from a molded plastic andcomprises a protruding portion sized and shaped to fit around the PCB.The protruding portion serves to support and protect the more flexibleand fragile PCB. The resulting assembly comprising the seal housing1501, seal 1503, PCB and PCB connector assembly 1505, and the sealretainer 1507 is referred to herein as a connector tube assembly 1515.

Turning again to the example of FIG. 43A, the tube is prepared forconnection to the connector tube assembly 1515. As shown FIG. 43A and ingreater detail in FIG. 43E, in step 1511, a portion of the secondelongate member at one end of the tube is separated from the firstelongate member. Then, in step 1513, a length of the separated secondelongate member is stripped away to reveal four conductive filaments (orthe number of conductive filaments contained in the second elongatemember). Step 1513 is shown in greater detail in FIG. 43F.

As explained in FIG. 43A and as shown in greater detail in FIG. 43G, theportion of the tube with the stripped length of the second elongatemember is inserted in the connector tube assembly 1515. As shown in step1517 of FIG. 43A and FIG. 43H, the four conductive filaments areinserted in the four terminals of the PCB. Then, as shown in FIGS. 43Aand 431, a bead of solder 1519 is placed over each filament-terminalconnection to secure the filament to the terminal and ensure a goodelectrical connection between each filament and its correspondingterminal.

To ensure that all pieces of the connector tube assembly 1515 aresecurely fixed to each other, a layer of glue 1521 is then applied. Glueis a broad term and refers to a material for joining, fixing, orattaching other materials. A glue can be adhesive or sticky to the touchwhen it is in a liquid or semi-solid state. When the glue has dried orotherwise cured into a solid state, the glue can be adhesive ornon-adhesive or non-sticky to the touch. The glue can be a resin, suchas an epoxy resin, or a thermoplastic elastomer (TPE). Use of TPEmaterials can be advantageous because they are generally flexible andcan accommodate twisting, bending, or pressure without shattering.

An example method for applying the glue 1521 is shown in FIG. 43J. Inthis method, a two-block mold is provided. In this example, the mold isstainless steel, however any suitable material can be used. Forinstance, the mold can be made from Teflon® PTFE blocks. One block isconfigured to accommodate the protruding PCB and PCB connector assembly1505 of the connector tube assembly 1515 and the adjacent tube, and theother block is configured to accommodate the opposite portion of thetube and connector tube assembly 1515. The tube is placed in thecompliant mold portions such that the blocks stack one on top of theother. A liquid glue is introduced into an inlet hole in the mold, andthe glue is allowed to harden. Then, the mold is removed to expose theglued tube-and-connector assembly 1523, which includes a layer ofhardened glue 1507 covering the PCB and the joint between the tube andthe connector tube assembly 1515. The glue layer can cover the PCB andall of the soldered connections on the PCB. In this manner, the layer ofglue can protect the PCB and the connections from corrosion. In otherwords, the glue serves three functions: sealing the connector and theconduit, holding the PCB in place and potting the PCB; the glue layerforms a pneumatic seal, a mechanical bond and a PCB pot.

Returning again to FIG. 43A, the tube-and-connector assembly 1523 isthen in condition for final assembly. As shown in greater detail in FIG.43K, a front clamshell 1525 and a rear clamshell 1527 are snappedtogether around the tube-and-connector assembly 1523 such that a portionof the PCB connector is left exposed. The clamshell 1525, 1527 portionscan be made of molded plastic or any other suitable material. Theclamshell 1525, 1527 portions serve to further protect thetube-and-connector assembly 1523 and to maintain the tube-and-connectorassembly in a bent position that promotes the return of condensate tothe humidifier unit when in use. As shown in FIG. 43L, the finalassembly can readily snap into a humidifier with a compliant electricalconnector near the connection port.

Although the foregoing manufacturing method has been described withreference to a flow chart, the flow chart merely provides an examplemethod for attaching a connector to the end of the tube that isconfigured in use to connect to a humidifier. The method describedherein does not imply a fixed order to the steps. Nor does it imply thatany one step is required to practice the method. Embodiments may bepracticed in any order and combination that is practicable.

Placement of Patient-End Connector with Electrical Connectivity

Reference is next made to FIGS. 44A-44H, which show an example connector1600 connecting one end of the tube 201 to a patient interface (notshown). The portion of the connector 1600 that connects to the patientinterface is indicated by reference 1601. FIG. 44A shows a sideperspective view of the connector 1600. As shown in FIG. 44B-44E, theconnector 1600 comprises a tube 201, a PCB 1603 and an insert 1605,designated together as a computational fluid dynamics (CFD) assembly1607 when assembled together, and a cover 1609. Each of FIGS. 44B-44Eshows a side-perspective view that generally corresponds with the viewof FIG. 44A.

The insert 1605 and cover 1609 are preferably molded plastic components.The insert 1605 can serve one or more of a number of purposes, includingproviding a receptor for the tube, providing a suitable conduit for thegas flow path, providing a housing for the PCB, and providing a housingfor a thermistor (discussed below). The cover 1609 protects and coversthe relatively fragile PCB and protects the connection between the tubeand the insert. As shown in FIG. 44A, the end of the insert 1605 that isinserted in the tube 201 is preferably angled to aid insertion into thetube 201. In addition, as shown in FIG. 44D, the insert desirablyincludes a stop portion 1606 that promotes correct placement of the tube201 with respect to the insert 1605 and also serves to protects the PCB1603.

To electrically connect the conductive filaments in the second elongatemember of the tube 201 to the terminals of the PCB 1603, a proceduresimilar to that shown and described above with respect to FIGS. 43E-431can be used.

FIG. 44F shows a cross section of the connector 1600 and generallycorresponds with the same side perspective view as FIG. 44A. FIG. 44Hshows a cross section of the CFD assembly 1607 and generally correspondswith the side perspective view of FIG. 44D. These figures show greaterdetails regarding the relative placement of the tube 201, CFD assembly1607, and cover 1609.

FIG. 44H shows a cross section of the connector 1600 taken along thewidth of the connector, as seen from the patient interface end 1601 ofthe connector, looking toward the tube (not shown). FIG. 44I shows aslide-plan cross section of the CFD assembly 1607 showing additionaldetails of the PCB and thermistor 1611. As shown in FIGS. 44H and 44I,the thermistor 1611 is placed into the flow path. The thermistor 1611can provide temperature and gas flow information to allow assessment ofthermal conditions near the patient interface.

Placement of Spiral-Style Connector

Reference is next made to FIGS. 45A-45E which show a connector withoutelectrical connectivity to a PCB. However, in some configurations, theconnector could be equally adapted to have electrical connectivity to aPCB. The connector is suitable for connecting to a patient interface ora humidifier. It is particularly suited for use as a patient-endconnector and/or device-end connector in an obstructive-sleep apneaenvironment.

A spiral-ended molded insert 1701 is provided. The end of the insert1701 opposite the spiral end is molded for insertion on or attachment toa humidifier port, and/or a patient interface port, and/or any otherdesired component.

As shown in FIG. 45C, the spiral end of the insert 1701 is screwed ontothe compliant turns of the tube 201. In this example, the spiral turnsof the insert 1701 are sized and configured to fit over and around theturns of the first elongate member 203 of the tube 201.

It should be noted that, in the case of a tube having one or moreelectrically powered wires therein, an electrical connection can beprovided on at least a portion of the insert 1701. When the insert 1701is installed, the electrical connector will preferably align with thewires, thereby facilitating electrical connection. Solder or the likecan then be used to secure the connection.

A soft rubber or TPE member 1703 can be inserted or molded on top of atleast a portion of insert 1701 and, optionally, tube 201 to promote theattachment between the insert 1701 and the tube 201. In some cases, theinsert 1701 (or at least the spiral end of the insert 1701) providessufficient lateral crush resistance to enable high-pressure moldingtechniques to be used, where the pressure can exceed the lateral crushresistance of the tube 201 without the insert 1701. Member 1703 can alsoadvantageously provide a soft surface to grip on when inserting andremoving tube from a component.

The foregoing method of attaching a connector to a spiral-wound tube isprovided by way of example. The method described herein does not imply afixed order to the steps. Nor does it imply that any one step isrequired to practice the method. Embodiments may be practiced in anyorder and combination that is practicable.

Placement of Alternative Device-End Connector

Reference is next made to FIGS. 46A to 46F which show a connector whichcan be used for medical circuits having electrical wires runningtherethrough. The connector 1801 comprises a cut-out 1802, which incertain embodiments is 30 mm (or about 30 mm) across. In certainembodiments, on one end of the cut-out 1802 is a L-shaped arm 1803 whichextends in part outward from the connector 1801 and in part parallel tothe longitudinal axis of the connector 1801.

The arm 1803 can have one or more electrical conductors 1804 embeddedtherein. The conductors 1804 can be made of copper or brass or anothersuitably conductive material and can be formed as flat L-shaped piecesrunning substantially along the length of the arm 1803.

The connector 1801 can further comprise an inner portion 1805 adapted tosit substantially inside a portion of the tube 201 and an outer portion1806 adapted to substantially surround a portion of the tube 201.

A portion of the second elongate member 205 is stripped away to revealthe one or more filaments 215 embedded therein. Preferably about 5 mm ofthe filaments 215 are revealed. The connector 1801 is then attached tothe tube 215 such that the inner portion 1805 sits within tube 201 andthe outer portion 1806 sits around the tube 201. Preferably theconnector 1801 is oriented such that the revealed ends of the filaments215 are located at or near the cut-out 1802.

The revealed ends of the filaments 215 are then electrically and/orphysically connected to the conductors 1804. This can be done bysoldering the ends to the conductors 1804, or any other method known inthe art.

A soft rubber or TPE member 1807 can be inserted or molded on top of atleast a portion of connector 1801 and, optionally, tube 201 to promotethe attachment between the connector 1801 and the tube 201.

In some embodiments, a substantially L-shaped elbow 1808 can be placedover the assembly. The elbow 1808 can provide some additional strengthto the connection and can provide a predetermined bend in the tube 201(such that the connector 1701 can tend to sit at an angle of about 90°from the body of the tube 201).

Coaxial Tube

A coaxial breathing tube can also comprise a composite tube as describedabove. In a coaxial breathing tube, a first gas space is an inspiratorylimb or an expiratory limb, and the second gas space is the other of theinspiratory limb or expiratory limb. One gas passageway is providedbetween the inlet of said inspiratory limb and the outlet of saidinspiratory limb, and one gas passageway is provided between the inletof said expiratory limb and the outlet of said expiratory limb. In oneembodiment, the first gas space is said inspiratory limb, and the secondgas space is said expiratory limb. Alternatively, the first gas spacecan be the expiratory limb, and the second gas space can be theinspiratory limb.

Reference is next made to FIG. 47, which shows a coaxial tube 801according to at least one embodiment. In this example, the coaxial tube801 is provided between a patient and a ventilator 805. Expiratory gasesand inspiratory gases each flow in one of the inner tube 807 or thespace 809 between the inner tube 807 and the outer tube 811. It will beappreciated that the outer tube 811 may not be exactly aligned with theinner tube 807. Rather, “coaxial” refers to a tube situated insideanother tube.

For heat transfer reasons, the inner tube 807 can carry the inspiratorygases in the space 813 therewithin, while the expiratory gases arecarried in the space 809 between the inner tube 807 and the outer tube811. This airflow configuration is indicated by arrows. However, areverse configuration is also possible, in which the outer tube 811carries inspiratory gases and the inner tube 807 carries expiratorygases.

In at least one embodiment, the inner tube 807 is formed from acorrugated tube, such as a Fisher & Paykel model RT100 disposable tube.The outer tube 811 can be formed from a composite tube, as describedabove.

With a coaxial tube 801, the ventilator 805 may not become aware of aleak in the inner tube 807. Such a leak may short circuit the patient,meaning that the patient will not be supplied with sufficient oxygen.Such a short circuit may be detected by placement of a sensor at thepatient end of the coaxial tube 801. This sensor may be located in thepatient end connector 815. A short circuit closer to the ventilator 805will lead to continued patient re-breathing of the air volume close tothe patient. This will lead to a rise in the concentration of carbondioxide in the inspiratory flow space 813 close to the patient, whichcan be detected directly by a CO₂ sensor. Such a sensor may comprise anyone of a number of such sensors as is currently commercially available.Alternatively, this re-breathing may be detected by monitoring thetemperature of the gases at the patient end connector 815, wherein arise in temperature above a predetermined level indicates thatre-breathing is occurring.

In addition to the above to reduce or eliminate the formation ofcondensation within either the inner tube 807 or outer tube 811, and tomaintain a substantially uniform temperature in the gases flow throughthe coaxial tube 801, a heater, such as a resistance heater filament,may be provided within either the inner tube 807 or outer tube 811,disposed within the gases spaces 809 or 813, or within the inner tube807 or outer tube 811 walls themselves.

Thermal Properties

In embodiments of a composite tube 201 incorporating a heating filament215, heat can be lost through the walls of the first elongate member203, resulting in uneven heating. As explained above, one way tocompensate for these heat losses is to apply an external heating sourceat the first elongate member 203 walls, which helps to regulate thetemperature and counter the heat loss. Other methods for optimizingthermal properties can also be used, however.

Reference is next made to FIGS. 48A through 48C, which demonstrateexample configurations for bubble height (that is, the cross-sectionalheight of the first elongate member 203 measured from the surface facingthe inner lumen to the surface forming the maximum outer diameter) toimprove thermal properties.

The dimensions of the bubble can be selected to reduce heat loss fromthe composite tube 201. Generally, increasing the height of the bubbleincreases the effective thermal resistance of the tube 201, because alarger bubble height permits the first elongate member 203 to hold moreinsulating air. However, it was discovered that, at a certain bubbleheight, changes in air density cause convection inside the tube 201,thereby increasing heat loss. Also, at a certain bubble height thesurface area becomes so large that the heat lost through surfaceoutweighs the benefits of the increased height of the bubble. Certainembodiments include these realizations.

The radius of curvature and the curvature of the bubble can be usefulfor determining a desirable bubble height. The curvature of an object isdefined as the inverse of the radius of curvature of that object.Therefore, the larger a radius of curvature an object has, the lesscurved the object is. For example, a flat surface would have a radius ofcurvature of co, and therefore a curvature of 0.

FIG. 48A shows a longitudinal cross-section of a top portion of acomposite tube. FIG. 48A shows an embodiment of a composite tube 201where the bubble has a large height. In this example, the bubble has arelatively small radius of curvature and therefore a large curvature.Also, the bubble is approximately three to four times greater in heightthan the height of the second elongate member 205.

FIG. 48B shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 48B shows an embodiment of a composite tube 201where the bubble is flattened on top. In this example, the bubble has avery large radius of curvature but a small curvature. Also, the bubbleis approximately the same height as the second elongate member 205.

FIG. 48C shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 48C shows an embodiment of a composite tube 201where the width of the bubble is greater than the height of the bubble.In this example, the bubble has a radius of curvature between that ofFIG. 48A and FIG. 48B, and the center of the radius for the upperportion of the bubble is outside of the bubble (as compared to FIG.48A). The inflection points on the left and right sides of the bubbleare about at the middle (heightwise) of the bubble (as opposed to in thelower portion of the bubble, as in FIG. 48A). Also, the height of thebubble is approximately double that of the second elongate member 205,resulting in a bubble height between that of FIGS. 48A and 48B.

The configuration of FIG. 48A resulted in the lowest heat loss from thetube. The configuration of FIG. 48B resulted in the highest heat lossfrom the tube. The configuration of FIG. 48C had intermediate heat lossbetween the configurations of FIGS. 48A and 48B. However, the largeexternal surface area and convective heat transfer in the configurationof FIG. 48A led to inefficient heating. Thus, of the three bubblearrangements of FIGS. 48A-48C, FIG. 48C was determined to have the bestoverall thermal properties. When the same thermal energy was input tothe three tubes, the configuration of FIG. 48C allowed for the largesttemperature rise along the length of the tube. The bubble of FIG. 48C issufficiently large to increase the insulating air volume, but not largeenough to cause a significant convective heat loss. The configuration ofFIG. 48C was determined to have the poorest thermal properties, namelythat the configuration of FIG. 48B allowed for the smallest temperaturerise along the length of the tube. The configuration of FIG. 48A hadintermediate thermal properties and allowed for a lower temperature risethan the configuration of FIG. 48C.

It should be appreciated that although the FIG. 48C configuration may bepreferred in certain embodiments, other configurations, including thoseof FIGS. 48A, 48B, and other variations, may be utilized in otherembodiments as may be desired.

TABLE 8 shows the height of the bubble, the outer diameter of the tube,and the radius of curvature of the configurations shown in each of FIGS.48A, 48B, and 48C.

TABLE 8 Tube (FIG.) 48A 48B 48C Bubble height (mm) 3.5 5.25 1.75 Outerdiameter (mm) 21.5 23.25 19.75 Radius of curvature (mm) 5.4 3.3 24.3

TABLE 8A shows the height of the bubble, the outer diameter, and theradius of curvature of further configurations as shown in FIGS. 50A-50C.

TABLE 8A Tube (FIG.) 50A 50B 50C Bubble height (mm) 6.6 8.4 9.3 Outerdiameter (mm) 24.6 26.4 27.3 Radius of curvature (mm) 10 8.7 5.7

It should be noted that, in general, the smaller the radius ofcurvature, the tighter the tube can be bent around itself without thebubble collapsing or “kinking.” For example, FIG. 50D shows a tube thathas been bent beyond its radius of curvature (specifically, it shows thetube of FIG. 50A bent around a radius of curvature of 5.7 mm), therebycausing kinking in the walls of the bubble. Kinking is generallyundesirable, as it can detract from the appearance of the tube, and canimpair the thermal properties of the tube.

Accordingly, in some applications, the configurations with increasedbending properties (such as those shown in FIG. 48A or 48B) can bedesirable despite having less efficient thermal properties. In someapplications, it has been found that a tube with an outer diameter of 25mm to 26 mm (or about 25 mm to about 25 mm) provides a good balancebetween thermal efficiency, flexibility, and bending performance. Itshould be appreciated that although the configurations of FIGS. 48A and48B may be preferred in certain embodiments, other configurations,including those of FIGS. 50A-50D and other variations, may be utilizedin other embodiments as may be desired.

Reference is next made to FIGS. 48C through 48F which demonstrateexample positioning of heating element 215 with similar bubble shapes toimprove thermal properties. The location of the heating element 215 canchange the thermal properties within the composite tube 201.

FIG. 48C shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 48C shows an embodiment of a composite tube 201where the heating elements 215 are centrally located in the secondelongate member 205. This example shows the heating elements 215 closeto one another and not close to the bubble wall.

FIG. 48D shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 48D shows an embodiment of a composite tube 201 inwhich the heating elements 215 are spaced farther apart, as compared toFIG. 48C, in the second elongate member 205. These heating elements arecloser to the bubble wall and provide for better regulation of heatwithin the composite tube 201.

FIG. 48E shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 48E shows an embodiment of a composite tube 201wherein the heating elements 215 are spaced on top of each other in thevertical axis of the second elongate member 205. In this example, theheating elements 215 are equally close to each bubble wall.

FIG. 48F shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 48F shows an embodiment of a composite tube 201where the heating elements 215 are spaced at opposite ends of the secondelongate member 205. The heating elements 215 are close to the bubblewall, especially as compared to FIGS. 48C-48E.

Of the four filament arrangements of FIGS. 48C-48F, FIG. 48F wasdetermined to have the best thermal properties. Because of their similarbubble shapes, all of the configurations experienced similar heat lossfrom the tube. However, when the same thermal energy was input to thetubes, the filament configuration of FIG. 48F allowed for the largesttemperature rise along the length of the tube. The configuration of FIG.48D was determined to have the next best thermal properties and allowedfor the next largest temperature rise along the length of tube. Theconfiguration of FIG. 48C performed next best. The configuration of FIG.48E had the poorest performance and allowed for the smallest temperaturerise along the length of the tube, when the same amount of heat wasinput.

It should be appreciated that although the FIG. 48F configuration may bepreferred in certain embodiments, other configurations, including thoseof FIGS. 48C, 48D, 48E, and other variations, may be utilized in otherembodiments as may be desired.

Reference is next made to FIGS. 49A through 49C, which demonstrateexample configurations for stacking of the first elongate member 203. Itwas discovered that heat distribution can be improved in certainembodiments by stacking multiple bubbles. These embodiments can be morebeneficial when using an internal heating filament 215. FIG. 49A shows alongitudinal cross-section of a top portion of another composite tube.FIG. 49A shows a cross section of a composite tube 201 without anystacking.

FIG. 49B shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 49B shows another example composite tube 201 withstacked bubbles. In this example, two bubbles are stacked on top of eachother to form the first elongate member 203. As compared to FIG. 49A,the total bubble height is maintained, but the bubble pitch is half ofFIG. 49A. Also, the embodiment in FIG. 49B has only a slight reductionin air volume. The stacking of the bubbles reduces natural convectionand heat transfer in the gap between bubbles 213 and lowers the overallthermal resistance. The heat flow path increases in the stacked bubblesallowing heat to more easily distribute through the composite tube 201.

FIG. 49C shows a longitudinal cross-section of a top portion of anothercomposite tube. FIG. 49C shows another example of a composite tube 201with stacked bubbles. In this example, three bubbles are stacked on topof each other to form the first elongate member 203. As compared to FIG.49A, the total bubble height is maintained, but the bubble pitch is athird of FIG. 49A. Also, the embodiment in FIG. 49A has only a slightreduction in air volume. The stacking of the bubbles reduces naturalconvection and heat transfer in the gap between bubbles 213.

Cleaning

In at least one embodiment, materials for a composite tube can beselected to handle various methods of cleaning. In some embodiments,high level disinfection (around 20 cleaning cycles) can be used to cleanthe composite tube 201. During high level disinfection, the compositetube 201 is subject to pasteurization at about 75° C. for about 30minutes. Next, the composite tube 201 is bathed in 2% glutaraldehyde forabout 20 minutes. The composite tube 201 is removed from theglutaraldehyde and submerged in 6% hydrogen peroxide for about 30minutes. Finally, the composite tube 201 is removed from the hydrogenperoxide and bathed in 0.55% orthophthalaldehyde (OPA) for about 10minutes.

In other embodiments, sterilization (around 20 cycles) can be used toclean the composite tube 201. First, the composite tube 201 is placedwithin autoclave steam at about 121° C. for about 30 minutes. Next, thetemperature of the autoclave steam is increased to about 134° C. forabout 3 minutes. After autoclaving, the composite tube 201 is surroundedby 100% ethylene oxide (ETO) gas. Finally, the composite tube 201 isremoved from the ETO gas and submerged in about 2.5% glutaraldehyde forabout 10 hours.

The composite tube 201 may be made of materials to withstand therepeated cleaning process. In some embodiments, part or all of thecomposite tube 201 can be made of, but is not limited to,styrene-ethylene-butene-styrene block thermo plastic elastomers, forexample Kraiburg TF6STE. In other embodiments, the composite tube 201can be made of, but is not limited to, hytrel, urethanes, or silicones.

Although certain preferred embodiments and examples are disclosedherein, inventive subject matter extends beyond the specificallydisclosed embodiments to other alternative embodiments and/or uses, andto modifications and equivalents thereof. Thus, the scope of the claimsor embodiments appended hereto is not limited by any of the particularembodiments described herein. For example, in any method or processdisclosed herein, the acts or operations of the method or process can beperformed in any suitable sequence and are not necessarily limited toany particular disclosed sequence. Various operations can be describedas multiple discrete operations in turn, in a manner that can be helpfulin understanding certain embodiments; however, the order of descriptionshould not be construed to imply that these operations are orderdependent. Additionally, the structures described herein can be embodiedas integrated components or as separate components. For purposes ofcomparing various embodiments, certain aspects and advantages of theseembodiments are described. Not necessarily all such aspects oradvantages are achieved by any particular embodiment. Thus, for example,various embodiments can be carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other aspects or advantages as can also be taughtor suggested herein.

Methods and processes described herein may be embodied in, and partiallyor fully automated via, software code modules executed by one or moregeneral and/or special purpose computers. The word “module” refers tologic embodied in hardware and/or firmware, or to a collection ofsoftware instructions, possibly having entry and exit points, written ina programming language, such as, for example, C or C++. A softwaremodule may be compiled and linked into an executable program, installedin a dynamically linked library, or may be written in an interpretedprogramming language such as, for example, BASIC, Perl, or Python. Itwill be appreciated that software modules may be callable from othermodules or from themselves, and/or may be invoked in response todetected events or interrupts. Software instructions may be embedded infirmware, such as an erasable programmable read-only memory (EPROM). Itwill be further appreciated that hardware modules may comprise connectedlogic units, such as gates and flip-flops, and/or may comprisedprogrammable units, such as programmable gate arrays, applicationspecific integrated circuits, and/or processors. The modules describedherein can be implemented as software modules, but also may berepresented in hardware and/or firmware. Moreover, although in someembodiments a module may be separately compiled, in other embodiments amodule may represent a subset of instructions of a separately compiledprogram, and may not have an interface available to other logicalprogram units.

In certain embodiments, code modules may be implemented and/or stored inany type of computer-readable medium or other computer storage device.In some systems, data (and/or metadata) input to the system, datagenerated by the system, and/or data used by the system can be stored inany type of computer data repository, such as a relational databaseand/or flat file system. Any of the systems, methods, and processesdescribed herein may include an interface configured to permitinteraction with users, operators, other systems, components, programs,and so forth.

It should be emphasized that many variations and modifications may bemade to the embodiments described herein, the elements of which are tobe understood as being among other acceptable examples. All suchmodifications and variations are intended to be included herein withinthe scope of this disclosure and protected by the following claims.Further, nothing in the foregoing disclosure is intended to imply thatany particular component, characteristic or process step is necessary oressential.

1.-59. (canceled)
 60. A cartridge for use with a humidificationapparatus, the cartridge comprising a chassis, one or more sensors, anda corresponding biasing member for each of the one or more sensors, eachbiasing member configured to couple the corresponding sensor to thechassis, each biasing member being interposed between the correspondingsensor and the chassis and adapted to provide, on insertion of the oneor more sensors into apertures in ports of the humidification apparatus,a repeatable force between an end of each of the one or more sensors andbarriers located within the apertures.
 61. The cartridge of claim 60,wherein the cartridge comprises a single one of said one or more sensorscoupled to the chassis at or proximate a first end of the cartridge, andtwo of said one or more sensors coupled to the chassis at or proximate asecond end of the cartridge.
 62. The cartridge of claim 61, wherein thefirst end and second end are located at opposing lateral ends of thechassis.
 63. The cartridge of claim 61, wherein the chassis comprises acentral connector portion, and a pair of wings that extend outwardlyfrom the central connector portion, said wings being perpendicular tothe connector portion.
 64. The cartridge of claim 63, wherein the pairof wings comprise the first and second ends, said pair of wings definingsockets for receiving the one or more sensors and/or the correspondingbiasing member.
 65. The cartridge of claim 60, wherein each biasingmember is adapted to compress when the corresponding sensor is insertedinto one of the ports, to provide a repeatable force directed outwardlyfrom the cartridge, to push the one or more sensors outwardly withrespect to the chassis.
 66. The cartridge of claim 60, wherein thebiasing member includes a spring.
 67. A humidification unit for use witha humidification apparatus, said humidification unit comprising ahumidification chamber, the humidification chamber comprising two ports,each port having an aperture therein adapted to receive at least one ofthe one or more sensors, the humidification unit further comprising thecartridge according to claim
 60. 68. The humidification unit of claim67, wherein a first of said two ports comprises a single apertureconfigured to receive a single one of said one or more sensors, and asecond of said two ports comprises an aperture configured to receive twoof said one or more sensors.
 69. The humidification unit of claim 67,wherein the cartridge is configured to be releasably mounted on thehumidifier chamber.
 70. The humidification unit of claim 67, thecartridge comprising a first end having a single one of said one or moresensors coupled thereto and a second end having two of said one or moresensors coupled thereto.
 71. The humidification unit of claim 67,wherein each biasing member is adapted to compress when thecorresponding sensor is inserted into one of the two ports, to provide arepeatable force directed outwardly from the cartridge, to push thecorresponding sensor outwardly with respect to the cartridge.
 72. Thehumidification unit of claim 67, wherein the biasing member comprises aspring.
 73. The humidification unit of claim 67, further comprising aflexible membrane, said flexible membrane being adapted to stretch withthe insertion of one of the one or more sensor to a repeatable forcedirected outwardly from the cartridge.
 74. The humidification unit ofclaim 73, wherein the flexible membrane is mounted in one or more of theapertures.